I run my system as below:
Asus P5K3 Deluxe | Q9300 @ 3.5Ghz - Scythe Ninja Cu | ATI 4870 512MB
2GB OCZ DDR3 1333 @ 1400Mhz | 2 OCZ 30GB CoreV2 SSD (RAID 0)
850W BeQuiet! | Antec 900 | 32 Bit Vista Ultimate | 16,178 3DMarks06
Have had it running like this for a few months now, no problems. I now have created a new underclocked setting in the bios for day to day use i.e. office and web browsing.
Works a treat.
All settings adjusted in the bios, not an Windows tool. Read the threads, I really only had to change the multiplier, fsb frequency and core voltage to get it working nicely.