well, if its win98, then its definitely out of warranty, and there is unlikely to be tech support available for an old model too (at least not free tech support).
does the hard drive whirrr? does the beeping continue, or just the normal beeps u always hear.
do what PeOfE and baseiber said if the beeps are not just the usual ones. Else, if the HD does spin, try a different monitor (if u have one or can borrow one) -- it could be the monitor and not the pc. hate to say it, but check the cables too. if the hd spins, and swapping monitors doesnt prove anything, throw a different video card (known to work) in it if u have access to one without going out and buting it.
open the box and look for any obvious electrical damage on the motherboard and video card (and any other circuitry). since it beeps, the power supply is probably good.