Today as I sat down I bumped my computer as it was on, the keyboard and mouse didn't work, I cheacked all connections but it was just frozen, I tried turning it off with the normal front switch but it did nothing, I had to use the main switch at the back of the tower (pentium 3). When I turned it back on nothing appeared on the monitor and it just beeps for 1 secind takes about 2 second rest the beeps again, I opened it up to see if anything came loose but could not spot anything, what happened? How do I fix it? Any help would be appreciated.