I have 3 private machines, (2 Desktop-Systems and a Notebook). I'm one of those persons who can't stand prebuilt systems (seriously, DELL, HP, FUJITSU... they all simply suck in performance and use code-protected hardware to avoid users exchanging computer parts... and therefore require you to call the stupid customer service if hardware crashes)... I build systems on my needs and usually have my machines for several years. "Operating System"-wise I always go for Linux, preferably Slackware Linux - as it's the most stable one and offers more freedom.
So... ahmm... I may present you my "youngest" and most powerful system:
Processor: i686, Intel Pentium 4, 3 GHz (I'd never again go for a Pentium though)
RAM: 2 x DDR-DIMM 512MB (1GB)
Harddisk: Hitachi Deskstar, ATA, 120GB
CD/DVD/CD-R: LiteOn LTC-5232K Combo 52x,32x,52x,16x
Graphics: ASUS V9570TD GeForce FX5700 (NVidia), 256MB DDR
Mainboard: ASUS P4S800 SiS648FX FSB800, 3x DDR333, 8x AGP, USB 2.0
Operating System: Slackware Linux 11
And... this is my desktop on that machine (KDE 3.5 with Superkaramba):
