The only operating system I regularly use at home (not for academic-releated stuff) is Windows XP. The only thing it doesn't do for me is test compatibility of applications with other operating systems, and it's by definition that it doesn't do that. Otherwise, it runs all my existing software (which non-Windows OS'es don't), runs them all well and without glitches (which Vista and 7 don't for all programs), and cooperates well with all my hardware (better than Vista, which my laptop was supposedly but probably not really designed for, and a bit better than 7).
I do have Windows Server 2008 R2, basically Windows 7 minus a bunch of the consumer features and plus a bunch of server features I don't use, installed on a second partition, but I rarely boot it up. The original purpose was to use the Russian Multilingual User Interface to improve my Russian skills, but I never did use it that much as it was more convenient to use XP where all my programs worked and were installed, and I no longer study Russian. I've considered deleting it several times, but it's survived so far. But if I do run low on space, it's in danger.
I also have a few virtual machines installed. The only ones I use with any frequency are PCLinuxOS MiniMe 2009 (despite its zero support/updates), mainly for Linux compatibility checking and seeing if there's any neat Linux software, and Windows 3.11/DOS. The latter is purely for anachronism's sake - I have one Windows 3.11 virtual box that supports high resolutions or lots of colors, and another that supports Internet browsing with IE5, Netscape 4, and Opera 3, as well as MP3 playback. My other virtual machines are, like Server 2008 R2 (Windows 7) in danger of deletion if space becomes an issue.
Technically I also use Solaris 9 at home, but it's for academic-related stuff, not because I actively choose to use Solaris 9. Most of the time I use it without a GUI, but occasionally I use GNOME 2.02 (a bit outdated, but I can't update it), and I formerly used the CDE with it, where the flagship Netscape 4.78 browser was available.
I agree with Genocidic Bunny on Apple/OSX - I've no desire to overpay for Apple hardware just to run their OS when it's the same hardware that any other company uses, and am not a fan of the company on principle reasons. Neither do I see any reason to replace my existing hardware that's working quite well, or acquire more physical hardware. But if it were easy and legal to run it on commodity hardware, it would be convenient to do so for compatibility testing.
That's a neat site. Don't remember how I first came across it, but I wouldn't have known how to get back there. Bookmarked now.
And then it kept a bunch of strange folders on my USB and some files I couldnt delete (it would error) but I got rid of those.
That annoyed me back when I occasionally had to copy files off my school's OS 9.2 Macs via floppy disks or flash drives. The Volume Settings Folder still exists on some of those disks.
Downsides - there's like 8 different versions, cost me $99, Comes with I.E. 8 which is still crap, more likely to get malware
You can actually uninstall IE in Windows 7 now, such that I'm pretty sure it won't start no matter what (as opposed to just being able to remove shortcuts but not the program in XP/Vista). And since you're free to install whatever browser you like, there's no reason to have IE on Windows 7 if you don't like IE.
Anyways, the Windows 7 downloads folder isn't hidden for me (might have been in Vista), and documents being hidden doesn't matter because of the documents library (or virtual folder, as it was called in the longhorn days before being cut from Vista).
