My newly upgraded rig keeps crashing

[An0tHerxNuMber]

Here are the specs:

Power Supply: XIGMATEK MC NRP-MC751 750W ATX12V

Motherboard: ASUS P5N-D LGA 775 NVIDIA nForce 750i SLI ATX Intel

Processor: Intel Core 2 Duo E6750 Conroe 2.66GHz LGA 775 65W Dual-Core

Graphics Card: EVGA 01G-P3-1281-AR GeForce GTX 285 1GB 512-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported

Ram: SUPER TALENT 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)

HDD: Western Digital Caviar SE16 WD2500KS 250GB 7200 RPM SATA 3.0Gb/s

Now, i just replaced the ram, g-card, and power supply, and the origional power supply i got was DOA unfortunantly but the other day i set up my rig using my old PSU to download ETW i had been playing some stuff and occasionally it would crash, a multitude of squares at angles and in many colors could apear on the screen blocking out the view and horribly lagging the computer, it would continue to run for a few seconds very poorly then usually die and restart alltogether, i assumed it was just because my graphics card was underpowered but today i received both the game and my new power supply and im still experienceing the random crashes, quite annoying does anyone know what could cause this?

 

[Langers2k7]

First thing I would do is remove the RAM, and reseat. Check there's no crud in the slots. Also, make sure one of your sticks isn't causing the problem by running them one at a time.

Check your graphics card is seated nicely and screwed in solidly, and check all your power connections are plugged in properly.

If you can, try the PC with another graphics card that you know works, and see if the problems persist.

 

[An0tHerxNuMber]

nothing, i tried a different set of ram, same problem occured