Crashing during gaming, vid card or PSU?

Hey all, system in sig might not be right...I got:
eVGA 7800GT and eVGA SLi mobo
165 opto running stock (troubleshooting)
and my Antec True 550 watt PSU.

The PSU is almost 5 years old. All rails are good except the 5v drops to 4.68...it's within 10% but could this be causing my problems? I wasn't having problems when I had AGP and a 6800GT. I noticed on my 7800GT I was plugging in 2, four-pin molex into one six-pin propietary molex on the 7800GT...but I was only putting in 2 5v pins and 4 grounds...so I think the 7800GT is running soley on the 5v rail which could be causing the drop.

I think it could be vid card because I do get some mild artifacting (running stock speeds on a factory OCed card...470 compared to 400 and I'm not sure but either 100/200mhz faster on RAM.

Thoughts?

I was running my bros computer on a cheapo 350w and the sucker only crashed mid way through games. Prime, memtest, superpi nothing crashed except in a game. So I swapped out it for a brandname 350w and it worked fine. Your situation sounds similar, I'd look into it. And if you go with a new Powersupply I recommend Zeus ST56ZF.

1. Run memtest86 first to rule out the RAM (RAM-related crashing is very similar to how power supply issues behave)
2. Use MBM5 or Speedfan to make a voltage level chart while games are running to see if the crash correlates with variations in the rails.

But you may also want to try supplying your video card with the correct power specs.

Might want to post what game is crashing, or is it all games? Some games are just buggy and a crash may be due to the software rather than hardware.