|It's going to depend on the beep codes for your particular model (you might want to post back with that information) but I googled ibm "continuous beep" and found a posting from an IBM user who said a continuous beep translated to a keyboard error. They replaced it with a USB keyboard and mouse and everything worked fine. It might even be something as simple as a stuck key.|
Again, the beep codes for your model may be different but that's something to start with.
Edit I found this too:
which says a continuous beep is a problem with the system board (motherboard). Not as easy a fix as replacing a keyboard. I don't know which models that page applies to.