My lovable compy:
CPU: Pentium 4, 2.53 GHz
Mem: 512 MB RAMBUS
Vid: 256 MB Radeon X1600 Pro
HD: 320 GB
OS: Win XP and Ubuntu

Just built this guy, nice system, runs smoothly.
CPU: Intel Core 2 Duo
Video Card: Nvidia 8800GT
RAM: 2 GB of DDR2 800 GSkill
OS: Windows XP Pro

Alright here goes:
AMD 64, 3500+
3 G RAM
Nvidia 7900GT
Sound Blaster audigy 2 ZS
300 GB HD
Vista x32

P5K Deluxe WiFi
Core 2 Quad Q6600 @ 3.6Ghz
MSI 8800GTS OC + OC
4x1 A-Data Extreme Edition DDR2 800 @ 1066 - Micron D9
Storage: 1.2TB

Asus P5N34-E SLI
Core2Duo E6400 (2,16GHz) 2,9GHz
4x1GB Patriot Extreme Performance 1066GHz
400+500GB Seagate Barracuda ES 32MB
1TB External Seagate
Asus 8800GTX
NZXT Tempest Case

MB: Shuttle AV49V/N
CPU: Pentium 4 2.8 GHz @ 2.98 GHz
RAM: 2 GB DDR
GPU: Radeon x1650 Pro AGP
SPU: Creative Audigy 4 (Non-Pro)
HDD1: 160 GB Internal - Hitachi
HDD2: 250 GB Internal - Western Digital
HDD3: 500 GB External - Phantom Drive (Samsung)
OS1: Windows Vista Ultimate SP1
OS2: Windows XP Professional SP3

My systems a few years old (except the GPU), still runs all the new games nicely. I'll be upgrading some time late next year.
Antec Solo + NeoHE-power
Abit KN8 Ultra
AMD Opteron 175 (dual core @ 2200 MHz)
2 Gb of 500 MHz DDR-memory
nVidia 8800GTS 640
1.5 Tb of hard-drive space over 3 Samsung-discs

CPU: AMD Athlon X2 4800+
Mob: Asus A8N32-SLI Deluxe
Ram: 2GB PC3200
GPU: GeForce 8800 GTS 640MB
Monitor: 24" BenQ, wide screen
HDD: Several which together amount to 2TB
Soundcard: Asus Xonar D2
Keyboard: Logitech G15
Mouse: Logitech MX Laser (x2 to never make running out of juice a issue)
Headset: Sennheiser HD 447
Speakers: Logitech X-540
OS: Windows XP SP3 (Got Vista Ultimate lying about but after a few months reverted back)

CPU: AMD Phenom X4 9950 Black Edition
RAM: 4 GB DDR2
GPU: Nvidia 8800GTX x2 SLI
HDD1: 300 GB Internal
HDD2: 200 GB Internal
HDD3: 500 GB Internal
OS1: Windows XP Pro

I built this system in December 2007 after seeing an article in TOTAL PC GAMING. I use it solely for playing games and I got most of the parts from www.overclockers.co.uk
Both the CPU and Graphics Card are not overclocked
Case: NZXT Apollo Advance Custom Gamer-Black
Samsung SM-226BW 22" Widescreen LCD Monitor - Glossy Black
Asus P5K Premium/WiFi-AP DDR2 Motherboard
Intel Core 2 Quad Pro Q6600 2.40GHz CPU
OCZ 4GB DDR2 Memory
GeForce 8800 GTX 768MB GPU
Creative Sound Blaster X-Fi Xtreme Audio 7.1 Sound Card
2 x Western Digital Caviar Blue 500GB SATA-II hard drives
O/S: Vista Home Premium 32 bit
Saitek Eclipse 2 Illuminated Keyboard - Blue/Red/Purple
Microsoft Sidewinder 2000dpi High Precision Gaming Mouse
Microsoft XBox 360 Controller For Windows

Intel Core 2 Duo 2.66GHz
2GB RAM
nVidia GeForce 7900GS
Creative SoundBlaster Audigy 2 ZS
900Gb HDD capacity
19" monitor (Native resolution of 1440x900)
All of the above primarily runs on Ubuntu Linux but I have Vista on the 2nd HDD for when I really need to use it! =)

I will soon upgrade my hardware, so I'll write both actual and what am I going to replace it for.
CPU: AMD Athlon 64 x2 4800+ --> AMD Phenom x4 9550
Graphics: MSI GeForce 6200 (tuned up to the level of 6600) --> Sapphire Radeon HD 4850
RAM: 2 GB Kingston DDR2 --> 4 GB
Sound: build-in Realtec AC97 compatible --> some old Sound Blaster Audigy (because it supports EAX)
OS: Windows Server 2008 (yeah, no kidding) and Arch Linux

My main PC,
Vista Ultimate
Intel Core2 Duo 3.16Ghz
3GGB ram
256 Meg gefroce 8600GT
Sound Blaster Audigy.
Other PC
Vista Pre.
Amd 64 x2 @ 1.8 GHZ
3ghz ram
256 meg Gefocre 7600GT OC
On board sound
PC 3
Vista Pre
Petium 4 3Ghz
2gzh ram
512meg geforce 7600
Sound blaster Audigy
Pc 4
Win XP
2Ghz Amd Sempron
1.5 Ghz ram
128Meg geforce 5200 fx
Sound Baster Live

Main PC:
Core 2 Duo E8400 3Ghz OC'd to 3.6Ghz
4GB 6400 RAM
OC'd HD 4850
X-Fi XTremeGamer
P5Q-Pro Mobo.
1.5TB HDD space.
22" ACER lcd.
Vista Ultimate 64.
Laptop:
Athlon 64x2 2Ghz
2GB RAM
ATi 1150 graphics.
160GB hdd.
15.4" screen.
Vista Premium 32

Intel Core 2 Quad 2.4Ghz
8GB RAM
Vista 64-bit
ATI 4870 HD
2x160GB HDD in RAID 0
80GB HDD w/ Linux (Ubuntu)