I have been in the business for about 5 years. What you are incountering can be fairly tricky to diagnosis. Remember to remove all external devices and PCI cards before starting this, because they could be causing the conflict.
1. Is it blue screening, if so then write down the stop error code. IE 0x0000007b can be a driver issue. Google search the code. You might hit on hardware that you have.
2. If if does a memory dump you can goto this article. Memory dump doesnt always mean bad memory. Could be a driver.
http://support.microsoft.com/default.aspx?scid=kb;en-us;315263
3. If you believe power, and I see that you have replaced the power supply. Dont forget the obvious. I have seen many old UPS's or surge protectors cause grief.
4. Smart technology communicates with the chipset on hard drives. If there is media defect are on the hard drive you might see Smart errors during post. That usually means your drive is out of tolerence and needs replaced. Lots of hard drive manufactors also have free downloads that you download and extract to a floppy and it will tell you if the drive is defective.
5. Memory can cause this issue also and if the board allows. Remove one stick and run the system if no crash the exchange for the other stick. If it crashes then there is the culprit
6. you might try a fresh load of the OS after formating the hard drive and not loading any software on it other then chipset drivers and video drivers and run it And see if it crashes. If no crash then install one program at a time testing for the period of time that it usually takes to crash the system.
Hope that helps
