Here's the Dell addy for the beep codes for that 4100:

http://support.dell.com/support/edocs/systems/dzuul/codemess.htm#post_beep_codes

Unfortunately, nothing is listed for 5 beeps. If and when it happens again, before "bumping" the 'puter, take a look at the back of the machine to see the diagnostic led lights and write down the colors (yellow or green) and the position (A, B, C, or D). Use that information to help diagnostic the problem. If it has been a while since you've done a little "house cleaning" inside that 4100, now would be a good time to have a look inside. Just remember to pull the power cord from the wall receptical and ground (touch) your body to the internal metal case before adjusting any cables or cards. Blow out all the dust, then reseat the video card and all the power and data cables before putting the side cover back on. If my memory serves me well, my old 4100 came with a nVidia chipset based video card and I got my video driver downloads direct from nVidia's web site...not from Dell. If you decide to do that, choose an earlier driver (41.09 is a good place to begin) from the Driver Archive.

Thanks for that. The four leds were green at the back, think I'll give it a good clean as you suggest. I'm not certain how many beeps I heard, thought it was five.