I use Ubuntu Studio 20.04.2 LTS inside a 64 bit machine. I also use VirtualBox 6.1 which I used to create a Windows XP SP3 virtual machine. But, when I get in that virtual machine (WinXP), I cannot to read or write any from the Ubuntu mounted HDD partitions. I'm specially concern about the My documents folder (music, images, videos, etc.), because the WinXP virtual machine doesn't see that folder or HDD. What I did wrong? How can I get to read and write into the Ubuntu My documents folder when I am into the WinXP virtual machine?
I have installed VirtualBox OSE on Ubuntu 11.04 and Windows XP pro as the virtual machine. Now I want to have a shared folder which can be accessed on both, my host Ubuntu machine, and my WinXP guest virtual machine.  How can I do that?
Is the harmonic oscillator potential unique in having equally spaced discrete energy levels? $2$ out of $3$ property of the unitary group In going through the review tool I often come across poor quality answers to poor quality questions. In particular, I will occasionally see questions that are simply asking for links to products, asking for tools, etc. Here are three examples that I've come across just this morning.        Clearly it's appropriate to go to the question and vote to close it (these are examples of not constructive) if they aren't already closed, but what should be done with the answers?    Should the answer be marked for deletion? Much of the normal reasoning for not providing link only answers is defeated if the question is simply asking for links. I'm tempted to mark them as 'looks good' for that reason, because it's the question that is flawed. Is that correct, or should I evaluate all answers as if they were responding to a quality question? Is there a way to view Google Chrome browsing history past three months ago? I'm trying to find a page I looked at months ago but it looks like it's disappeared off the face of the planet. I thought I would have better luck looking through my Google Chrome browsing history, but I can't see history past September. Can I force Google Chrome to display history further into the past? Can I retrieve the history manually from a directory? Is the history data gone? What sci-fi work first showed a weapon of galactic-scale mass destruction? Currently, I have two examples in my mind:   Halo (Halo video game series; 2001): Can destroy all sentient life within three galactic radii The Moment/ Eye of Discord/ Galaxy Eater (Doctor Who (2005) TV series; 2013): Can destroy entire galaxy within a moment   What sci-fi work first showed a weapon of galactic-scale mass destruction? With the announcement of the detection of gravitational waves, questions about the implications proliferate.  Some relate to the possible existence of gravitons.  The analogous relationship between gravitons/gravitational waves and photons/electromagnetic waves is frequently mentioned.  The detection of individual photons required experiments of very low intensity light, yet their existence was inferred (prior to their actual detection) by Planck and Einstein (among others) using the properties of experimental black body radiation and the photo-electric effect.  If the prospects for detection of gravitons requires similar study of very low intensity gravitational waves, then those prospects are very dim indeed. My question: are there similar indirect "experimental" methods for inferring the existence of gravitons? Showing group with $p^2$ elements is Abelian I have a group $G$ with $p^2$ elements, where $p$ is a prime number. Some (potentially) useful preliminary information I have is that there are exactly $p+1$ subgroups with $p$ elements, and with that I was able to show $G$ has a normal subgroup $N$ with $p$ elements.   My problem is showing that $G$ is abelian, and I would be glad if someone could show me how.   I had two potential approaches in mind and I would prefer if one of these were used (especially the second one).   First: The center $Z(G)$ is a normal subgroup of $G$ so by Langrange's theorem, if $Z(G)$ has anything other than the identity, it's size is either $p$ or $p^2$. If $p^2$ then $Z(G)=G$ and we are done. If $Z(G)=p$ then the quotient group of $G$ factored out by $Z(G)$ has $p$ elements, so it is cylic and I can prove from there that this implies $G$ is abelian. So can we show theres something other than the identity in the center of $G$?  Second: I list out the elements of some other subgroup $H$ with $p$ elements such that the intersection of $H$ and $N$ is only the identity (if any more, due to prime order the intersected elements would generate the entire subgroups). Let $N$ be generated by $a$ and $H$ be generated by $b$. We can show $NK= G$, i.e every element in G can be wrriten like $a^k b^l $. So for this method, we just need to show $ab=ba$ (remember, these are not general elements in the set, but the generators of $N$ and $H$).   Do any of these methods seem viable? I understand one can give very strong theorems using Sylow theorems and related facts, but I am looking for an elementary solution (no Sylow theorems, facts about p-groups, centrailzers) but definitions of centres and normalizers is fine. Mysterious cord running from wall. Safe? My wife and I are preparing to sell our home and are discovering some weird things. Our home was built in 1958, so it is older. We found this in a corner that had some furniture in front of it.   We are wondering    What kind of wiring is this?  Is it safe to handle or remove? Does Two-Face die at the end of The Dark Knight? How can I attach a file to a post? I want to attach some files to a post on one of Stack Exchange sites. What is the best way to do this? Where can I find out about Stack Overflow history? I'd like to know how Stack Overflow and other sites started - which was first, who initiated it (OK, that's on the link below) and why, how the different sites evolved, how the rules evolved, etc.  Where can I find such information?  Of course, I know I can look at  for a brief overview but I'm wondering if there is info on this site, particularly more detailed.. Children’s books, one in space setting, the other in a jungle We have a system hosting many websites for our customers, and inside that system there is a method that non-live customers can view their sites before we turn them on.  Say the link is something like this: ourbigcompany.com/customer/domain=thisisanewsiteurl  Those links are not linked to anywhere outside a secure login - they are only sent to the customer via email. They are publicly viewable, as they have to be, but that's not the real problem.  The real problem is that somehow Bing is getting hold of them and trying to crawl the sites.   I know how to stop the crawling, but that would be like treating the symptoms without fixing the problem.  We log the traffic and there is no referrer - so that is not helpful.  If I change the querystring value for a site, Bing has it within hours. I need to figure out where Bing is getting the links from so that I can close what is obviously a security hole, but I am not sure how.   Any ideas on how to figure that out? How to increase body height? I am an adult, and I want to be taller. I know about many medicines which claim to treat stunted height.  Is there any truth behind these? How to delete pre-installed apps in Catalina? I want to delete the pre-installed apps, like Music, Books, Siri etc. from my iMac running Catalina. How do I do this?  (NOTE:  asks the same thing but was closed as a duplicate of . Annoyingly, the supposed duplicate doesn’t give an obvious answer to the question, and the original was locked can’t be answered, hence a new question. I can’t add an answer to  either) How to move windows that open up offscreen? I have a dual monitor setup, and I recently played around with the positioning settings, and some of my single window applications do the favour of preserving where they were last closed, and opening in the same position later. Unfortunately, that now places them out of the viewable area of my screens!  Is there some way to force a particular window into the viewable area? New mobile chat doesn't follow the keyboard height The Japanese keyboard on iOS dynamically changes it's height to show suggestions and hides the input box of new mobile chat.        Additionally, third-party keyboards make the input box completely hidden. The chat seems to treat third-party keyboards as having no height.        iOS 9.2.1 / Mobile Safari  There is no problem in old (stable) design but it doesn't fix the input box to bottom! Why is my network interface named enp0s25 instead of eth0? A lot of my scripts stopped working after installing Ubuntu 15.10 and I have trouble remembering this new name as I was used to ethx and wlanx for years. Is there a reason for this change? Do I have to get used to this or can I just rename it and go back to good old eth0?  $ ifconfig  enp0s25   Link encap:Ethernet  HWaddr 77:5a:5e:a6:86:d5         inet addr:192.168.31.239  Bcast:192.168.31.255  Mask:255.255.255.0       inet6 addr: fe80::725a:b6ff:fea6:86d7/64 Scope:Link       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1       RX packets:4833 errors:1332 dropped:0 overruns:0 frame:666       TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0       collisions:0 txqueuelen:1000        RX bytes:3266446 (3.2 MB)  TX bytes:1046654 (1.0 MB)       Interrupt:20 Memory:d3500000-d3520000 Here's an image from another question:    I get what the pull down resistor is there to do, but I don't really understand exactly how it works.  When there is no voltage applied through the base wire, why does any induced current then go through R2, but when a voltage is applied, it goes to the transistor? My understanding is that voltage always follows the path of least resistance, so if applying say, 5v turns the transistor on, that means that the transistor has a lower resistance than R2, so I would also assume any induced current would also flow through the resistor - so why does it then go through R2? Is a semigroup with unique right identity and left inverse a group?