Problem with my M2N-SLI deluxe motherboard

[Atlantean]

I have 3 gbs of ram in my motherboard currently (3 1 gb sticks) and I was going to remove one and just have 2 because 3 doesn't seem to make that much of a difference (I am running vista). I have them set up that the dual channel ocz sticks are in slot A1 and B1 and the single stick is sitting in slot B2. I went to take out the single stick the other day and when I booted back up all the computer would do is beep at me. One long beep followed by two short ones. I really can't see a reason why this would be happening, it also didn't seem to want to boot to windows when I got the beeping to stop. Anyone know what might be causing this problem?