Saw someone on here earlier this week with this problem. Turned out his RAM wasn't seated all the way. It would help to know more about your system. I'm going to assume you have 2 sticks of 2 GBs. Take one stick out, can you boot successfully? If so, put it back in and make sure it's seated all the way. Now try to boot.
If that doesn't work, tell us: CPU, RAM, PSU, Motherboard, OS. Basically, the more info you give the easier it will be to help. Is this a new build?
Other things to check:
1. Are you sure your RAM is in the right slots?
2. Download memtest86+ and burn it to a bootable CD. With one stick in your system, run memtest86+ for a few hours or better yet overnight. If it doesn't have any errors, take it out, put the other in, now run memtest86+ on that stick. If it doesn't have nay errors, put both in and run it again.
Thank you for the reply. I think I know what the problem is. I tried installing 1 2gig chip at a time in the A1 slot and neither worked. I tired installing both in the A1 and B2 slots as dual channel and neither worked. I then installed 1 in B1 slot and it worked. Took it out and installed the other in the B1 slot and it worked. I then installed 1 in the B1 and one in the B2 slot and both are recognized as single channel but it is recognized as 4 gigs. I found a scratch on my motherboard where I must have scratched over a trace when installing the cpu and fan. Those traces go to the memory slots. I bet I F'd up my Motherboard.
Well The 4 gigs is working fine as single channel. I think I wont bother with returning the motherboard. Unless I can be convinced that dual channel is that much greater than single channel configuration.