I just add another 8800gts 320mb today for sli so i could play high on crysis but everytime the map loads in single player i click for start and it crashes right after it shows the graphics. It shuts down to computer to be more specific. This is frustrating as i just want to play. I have a ASUS m2n-sli delux, AMD Brisbane 3600+, G.SKILL 2GB (4 x 1GB) DDR2 800 (PC2 6400) and Antec 550w true power 2.0.
 
Do you think its my power supply and would the instant crashing after map load be a symptom? I could play with 4gb memory before with one card so i should be able to with Sli.

Yes, your PSU is far too weak for two G80 core 8800's.  Also, you may want to do a thorough uninstall of your graphics drivers before installing new ones.