Windows PC hangs

I bought a PC assembled by myself about two months ago. PC configuration is mentioned below. After a month from my purchase, my PC hangs whenever its processing goes high ( If I use some IDE with Tomcat servers and Java VM ) or if I play any good resolution video. After getting hanged, it usually doesn't respond and only way to get outta this hanged situation is hard reset. Can any one help me resolving this problem ?
  • AMD FX6100 Processor
  • ASUS M5A78LMX3 Motherboard
  • TOSHIBA 1GB SATA Harddisk
  • TRANSCEND 8GB DDR3 RAM
  • GIGABYTE 730 2GB Graphic card
  • OS - Windows 7 ultimate x64
Thanks in advance.
 
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