Installing a HD on an OLD computer

I have a friend with a really old 486 intel machine. He has a 340 meg hard drive which is really full. He doesn’t have very much money so I thought I’d be nice and buy him a new drive. I got a WD 1.2 gig drive pretty cheap off of Ebay and went toinstall it. Alas, his bios only recognizes drives up to 540 meg. I’m looking for the easiest and cheapest way to get this drive working.