Don't forget you need the speaker connected to hear any beeps (did it beep before, from the speaker?). Don't wanna sound patronising btw - just in case!
Also, I had a mb inexplicably die on me once, and clearing the CMOS sorted it out. There may be a "clear CMOS" set of jumpers on the mb somewhere, you would probably have to move the jumper connector across from where it is to the next set of pins, leave it for a few seconds, then move the connector back to where it was. If you don't have a manual see if you can find any reference or model numbers/names on the mb to Google for to see if you can get a manual online, which will show you where this jumper is if it has one.
