Newbie - Help please

I pushed the 'sleep' button on my MS wireless keyboard and the computer then didn't wake up. I made sure the button wasn't stuck down, changed batteries, moved computer - nothing. It would start but wouldn't display anything - no setup screen, no beeps nothing.

My mate came over and ended up removing a battery - looked like a silver coin and then replaced it. The computer then worked. I had some weird messages upon start up like 'Express Gate not installed' and Adaptor 1 HDD not detected. I had to disable IDE and express gate to get rid of these messages - worked.

I did some checking on Google and think I got it all back to normal. As wierd as it sounds the computer just seems to be running a little bit slower. I have no idea if it's just me. How many of the SATA's should be in use etc? Should have I disabled the IDE etc.

WTF happened with the sleep button?! I have only just got a computer, I havnt used one in about 10 years...