Before going any further.. you test the 80GB on another system to make sure there is no problem in the drive itself.

here is the link from where you can download new year 2002 bios
*www.pcchips.com.tw/PCCWeb/Downloads/ProductsDetail_Download.aspx?DetailID=45&DetailName=BIOS&DetailDesc=M748LT(V3.x)&MenuID=35&LanID=2
Please make sure the model number matches your motherboard.
(I take no guarantee for this)

Unfortunately this is a BIOS limitation only and no other alternative apart from changing the motherboard iteself (to intel 810i).
SO there is no option but to flash the BIOS.

Read the instructions on the website carefully.