1: If you are able run the PC for a while, restart the computer, enter the BIOS then check the temps and voltages.
2: Download and run HWMonitor http://www.cpuid.com.../hwmonitor.html provide a screenshot of the readings with your next reply.
3: Download Speedfan and install it. Once it's installed, run the program and post here the information it shows. The information I want you to post is the stuff that is circled in the example picture I have attached.
If you are running on a vista machine, please go to where you installed the program and run the program as administrator.
(this is a screenshot from a vista machine)
To capture and post a screenshot;
Click on the ALT key + PRT SCR key..its on the top row..right hand side..now click on start...all programs...accessories...paint....left click in the white area ...press CTRL + V...click on file...click on save...save it to your desktop...name it something related to the screen your capturing... BE SURE TO SAVE IT AS A .JPG ...otherwise it may be to big to upload...
then after typing in any response you have... click on browse...desktop...find the screenshot..select it and click on the upload button...then on the lower left...after it says upload successful...click on add reply like you normally would.
Screenshot instructions courtesy of happyrock
Post your PSU details brand, model and output please.