Custom Desktop Freeze>Flashing Underscore>Blank Screen

Hey Guys

I built a desktop around 5 years ago and have kept upgrading its hardware. A while ago I had an incident where the screen froze. I left it for a while hoping it would come out since I had some important stuff I was working on. Eventually I did a hard restart. When it rebooted, I got the bios and then a black screen that flashed an underscore character. I had previously had a problem with a RAM stick being corrupted so I started removing/reinserting RAM to try an identify the source problem. I removed the last one and, even after reinserting the RAM in all possible combos, all I get is a no connection on my monitor, and three beeps, no loop, about a second each. If I remember correctly, it is an ASUS motherboard with an AMD Phenom 2 Black Box processor, updated around 2 years ago. I am using my original hard drive. Graphics card is Radeon Sapphire 6950, but I tried using the on-board graphics to no avail. I think I know what the problem is but am short on money so I want some backup opinions before I start replacing stuff.

VR