Rebuilt my machine in March 2009 with the following kit:

Intel Q6600 G0 SLACR 2.4GHz overclocked to 3.2GHz

Managed to pick up a cheap Q6600 / motherboard / RAM combo on eBay, so took the big quad core leap. Was lucky to get one that overclocks this far on stock voltages with a big fat Xigmatek HDT-S1283 cooler.

Gainward ATi Radeon HD4850 512MB PCIe

This is standing up OK currently (May 2009) but is a bit weak in newer titles @ 1920x1080. Hopefully it can last until late summer when the next big wave of AAA games hits.

OCZ DDR2 PC2-8500 Reaper HPC Edition 2x 2GB

This has been MUCH better than my Corsair Dominator XMS2. It clocks a bit further easily at stock voltages.

Gigabyte EP45-UD3P

Nice overclocking options, would not have been my personal choice, but is better than my old abit.

ThermalTake ToughPower 750W PSU

I really like this PSU - the modular connectors are great.

Creative X-Fi Fatal1ty

This one came as a surprise too - Creative have actually made a card that does not give me a whole series of problems! The original drivers are buggy on my system, but recent drivers solve the issue (drop-outs in the audio during heavy HDD access, e.g. game levels loading).

Old hardware

ThermalTake Xaser case

Turns out this was causing me heat problems - don't try to put a P4-style style in a pre-P4 case!