Download memtest86 and follow instructions... burn to cd and boot from cdrom. Run memtest on pc for at least 6 hours (12 to 24 is recommended). Also check motherboard manufacturer for recommended mems - possible incompatibility problems.
When booting in safe mode, run disk error checks to detect bad sectors. If you use seagate, download the Seatools diagnostics.
Drivers/hardware conflicts are harder to diagnose. Did you add any new hardware to the computer or install a new program? What is your power supply/PSU?