Random Restart Troubleshooting HELP

Hi All,

I have this problem with a system I built myself and cannot figure out what is going on (sorry if this is in the wrong forum). This problem happens (seemingly) randomly. If I am playing WoW and watching a video (i.e. hulu/netflix) simultaneously, sometimes my computer will freeze. First my display will go black--i.e. no signal to monitor. Then my computer will do something even weirder. It will give me 5 beeps and then lock up. Sometimes this will happen if I'm just playing Skyrim after awhile, but not always. Obviously this happens while I put stress on the comp but I cannot seem to pin down the issue.

The only way to restart the computer is to do a hard restart. I have no idea what the problem could be. This has been happening for a couple of months now, but I really want to get to the bottom of it. I'm currently doing a stress test (few hours so far without any problems) -- Prime95. I also did a FurMark stress test for my GPU without any problems. Any ideas? PSU maybe? Haven't done a RAM test yet. My temps seem a little high but fine: CPU below 60c, Core 1&2 below 77c (taken with speedfan while doing this current Prime95 stress test).

Here are my specs:

CPU: Intel Core i5-2500 Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 2000 BX80623I52500

GPU: SAPPHIRE 100315L Radeon HD 6850 1GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity

RAM: 4b (total) G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)

PSU: CORSAIR Enthusiast Series TX650 V2 650W ATX12V v2.31/ EPS12V v2.92 80 PLUS BRONZE Certified Active PFC High Performance Power Supply

MB: ASRock P67 EXTREME4 (B3) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

HDD: SAMSUNG Spinpoint F3 HD103SJ 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

OS: Win 7 64bit

Case: COOLER MASTER HAF 922 RC-922M-KKN1-GP Black Steel + Plastic and Mesh Bezel ATX Mid Tower Computer Case

Any help y'all can provide will be appreciated. Thanks! Let me know if you need more info.