|It could be one of a number of possibilities:|
- 420W power supply is undersized for your system. Please list make/model & detailed amperage specs
- overheating CPU. Please list CPU temp.
- bad or improperly configured RAM. Please list make/model/specs plus the speed & voltage you're running it at. Test RAM with memtest86 or Windows Memory Diagnostic.
- virus or malware infection. Have you run a full virus & malware scan, preferrably from Safe Mode? Which anti-virus program do you have?
Have you made any changes recently, either software or hardware, that may have brought this on?