I would suggest giving all your hardware a good workout to stress test it all. I have often used
BurnInTest in the past to do this. The free trial will run a test for up to 15 minutes, but the paid version will run it for as long as required.
If you find the OS is unstable then it may be worth creating a bootable OS CD (details on how to create this can be found on their website
Here).
Mark.