My desktop is Windows 7 Home Premium.
My portable computer is a Raspberry Pi Model B that runs Raspbian, XMBC, and MinePeon.
Right now, I'm really close to turning it into a laptop.

Also, just for fun, here's my work desktop:


Work Desktop by elfprince13, on Flickr

That's a pretty epic wallpaper of that one movie. JOHN something or another.

John Carter. One of my favorite movies of the last few years. I'm still really upset at how badly Disney botched the marketing, thereby ensuring we wouldn't get any of the sequels.

Windows 8.1 Pro with Media Center
I have VS2013 Ultimate, Windows SDKs, Adobe CS5.5 (academic license), Lightroom, LaTeX, LibreOffice, a few games (e.g. Portal), and other miscellaneous software.
The desktop is also a DVR with 3 digital cable TV tuners. Windows Media Center is the DVR application. I have never noticed any performance impact when recording TV.

Intel i7 3770K 4 Cores, 8 Threads @ 3.5 GHz
16 GB RAM
256 GB SSD
GeForce GTX 650 Ti with 1 GB RAM
4 TB RAID 5 (2 TB x 3 disks)
4 x USB 3.0 ports, with lots of USB 2.0 ports
Connected to Gigabit Ethernet LAN backbone
1500 V⋅A UPS with 2 x 12 V 9 A⋅hr batteries in series

3 screens:
1920 x 1200
2048 x 1152
1680 x 1050

Needless to say, this computer is very fast.

Yeah, I who am used to slow computer would say XP on 512MB would be a dream. I second what CVSoft said (though I'm crazy enough to run XP on 256MB). And a hard drive to mach those specs (about 20-40GB) should be easy and cheap to find on eBay...
[EDIT] Oh, perhaps you meant a CD drive. Hmm.

Linux Mint 14
1024 MB RAM
1280*800
4 minute battery
Minecraft runs: 310 MB 30 fps
My background? I don't have one...

Well, I'm currently running Windows 8.1 (Oh this is a laptop, I don't have a desktop), general specs are:
6GB RAM, 2GB Nvidia GT610M Card, 1366*768 display (720p), 5 hour battery life, 24GB SSD for Intel Rapid Start Caching and what not, and a 1TB HD (7200RPM).

This is my normal desktop:

My desktop:

Very nice, naib. I'm trying to figure out what the code in the background is; it's clearly for a game of some sort, but I can't get much past that. Do you have any idea what it is?

It looks like the DOOM source code, from my experience of it.

New wallpaper:

I like the change up in this topic, elfprice; as soon as I take the rest of my stuff out of boxes from painting I'll post my new get-up as well.

Tada:

I like this new trend.
Orangey monitors = f.lux
white thing = tablet pen

We definitely used to have a dedicated topic for this variant, but I couldn't find it anywhere so I hijacked this one

Cramming everything into one picture wasn't easy. And yes, those are both Windows XP (PentiumII and a Sun desktop I don't use very often). The remaining computers either run Windows 7 or Solaris. The widescreen monitor is on an 8-port KVM switch, connecting the three desktops on the desk and the laptop.

My desktops are just so crazy now... I have:
- Ubuntu 14.10 with Unity (transparency on the top bar)
- Windows 8.1 Professional (jet-black window borders)
- Windows 10 Technical Preview (looks like Windows 8.1 gone wrong)
- Windows Server 2012 Datacenter (on a laptop... with Halo installed)
- Windows Server 2008 Datacenter (Windows Classic, because I can't seem to get the Vista theme)
- Windows Vista Enterprise (VMware Player)
- Mac OS X Leopard (in command line, because I can't get the stupid Hackintosh to work right...)
- Windows Vista Business (at factory defaults... which is out of character for me)
- Windows 7 Professional (see above)
- Windows 8.1 Embedded Industry Pro (on a netbook)
- Windows XP Professional (Oracle VirtualBox, looks like Windows 7 with RocketDock)
- Windows 95 (on an ancient laptop)
- Linux Mint 20 (on another old laptop)

Do you think I have too many computers?

No... I don't think you have too many computers... Though I don't have a desktop that can fit them all, I have the following:
- Windows 3.1 (on an ancient laptop, with Calmira II installed so it looks like 95)
- Windows 95 (on an ancient laptop)
- Windows 98 (on an ancient laptop)
- Windows 2000 Pro (on an ancient desktop)
- Windows XP Home (on an ancient desktop)
- Windows XP Professional (on an ancient laptop)
- Windows Vista Business (on just a laptop)
- Windows Vista Home Premium (on a nicer gaming-capable laptop)
- Windows 7 Professional (on just a laptop)
- Windows 7 Professional (on just another laptop)
- Windows 8.1 (on just another desktop)
- Windows 10 Technical Preview (it's buggy and not used much)
- Mac OS X Mavericks (still hasn't gotten to the HDD, because I can't get the stupid Hackintosh to work right...)
- ArchLinux (on a netbook with a crushed screen)

All but 2 of those are on independent hardware (OS X and WinTechPreview are dualboots), a lot I stuff under my bed or in a big box and in a crate on my worktable.
Do you think I have too many computers?