Blu-ray PC keeps restarting

[GCW2216]

Hello, I need your help.

I built a PC to support Blu-ray playback. Here are the specs.

IN WIN IW-BT611T.300SL Silver Best Performed 0.8mm SECC Japanese Steel metal MicroATX Desktop Computer Case 300W Power Supply

GIGABYTE GA-MA78GM-S2H AM2+/AM2 AMD 780G HDMI Micro ATX AMD Motherboard - Onboard HDMI and ATI HD 3200 graphics

AMD Athlon 64 X2 4000+ Brisbane 2.1GHz 2 x 512KB L2 Cache Socket AM2 65W Dual-Core Processor

Crucial Ballistix 2GB 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Desktop Memory - 512MB dedicated to onboard video

LITE-ON Black 12X DVD-ROM 32X CD-ROM SATA Blu-ray DVD-ROM Drive Model DH-4O1S-08

I have the machine connected to a 23"LCD via HDMI - I am using Power DVD 7.3 to play the BD's because thats what came with the drive. I can sit at the top menu for as long as I want, as soon as the movie attemps to play, once it's past all the copyright warnings, the machine restarts.

Any ideas? Your help is appreciated.

Thank you