Upgrading

I am running an AMD Athlon 900 / GA 7ZMM M/board, Socket A, via KM133 Chipset, 400w power supply in a midi tower and the m/board is dead.I wish to get a new m/board BUT don’t know which one to get. I have SDRAM, AGP Video card,
40gb seagate HDD i want to use them with the new M/board without getting a bigger tower if possible. As FUNDS are limited i can’t afford the rolls royce type. I just want a good reliable m/board priced in the low-medium price range. Any suggestions greatly appreciated.