http://www.memtest.org/
You need to scroll down the page until you see the three blue screenshots. Just below is the list of downloads for Memtest86+ V4.20. Click on Download - Pre-Compiled Bootable ISO (.zip)and save to your desktop, When the download is complete right click the file and select Extract Here and burn the image to a CD. In windows 7 right click the extracted file, select Open With, then select Windows Disc Image Burning Tool then follow the prompts. For all other versions of windows (if you do not have an ISO burner) download this free software. http://www.isoimageburner.com/
Boot the PC into the Bios setup and set the CD/DVD drive to 1st in the boot sequence. Insert the disk in the drive then reboot and the disc will load into dos. Leave the test to run through at least 8 cycles.
The memtest will not be 100% accurate but should easily detect any major faults.
For windows XP - Click on Start and then Run. Type verifier into the box and hit the Enter key.
For Vista and Windows 7 - Click on Start and type verifier into the search box then click on verifier in the list that pops up.
Driver Verifier Manager will open.
Select the first choice "Create Standard Settings" and click on the "Next" button.
Now select "Automatically select all drivers installed on this computer" and click on the "Finish" button.
A box will appear asking you to restart the PC for the changes to take effect. Click on "OK" and reboot the PC.
To stop Auto reboot so you can read the error message do this for Windows XP:
Click the Start button, right-click My Computer, click Properties, click the Advanced tab, and then click Settings under Startup and Recovery.
Under System Failure, uncheck the "Automatically restart" check box.
And do this in Windows 7 and Vista:
Click Start, select 'Control Panel' select 'System' in the left pane select 'Advanced System Settings' in the box select the 'Advanced' tab then under 'Startup and Recovery' select 'Settings.' In the box under 'System Failure' uncheck 'Automatically Restart'.
If the PC reboots normally then there is no problem with any of the drivers. If you get a blue screen straight away it will name the faulty driver. If you are absolutely certain that the named driver is OK then make a note of it.
You will then have to go back into the Verifier and instead of selecting all drivers select "Select drivers from a list". Click on "Next" and the list of drivers will appear. Select them all apart from the one you know to be OK. Click on "Finish" and reboot.
Once you have identified the faulty driver or confirmed that there are none go back to the first page of the Driver Verifier Manager and select "Delete Existing Settings" and click on "Finish"