With any install, it helps to give us as much info as you can. Computer manufacturer, MB make and model, CPU.....
If the MB is too old, it may not be able to even recognise the hdd without flashing a newer BIOS, assumming that one is available. I'm going to guess that the 4 gig hdd is the original one that came with the PC. So it's probably like a Pentium 2 based PC...which means that you are going to have to flash the BIOS to get it to read anything like 16gigs and up. Look ok the MB for a model number or if its like an HP or something, check and see if they have a BIOS update on their site.
-Alternatively-
If You don't want to mess with flashing the BIOS, I'd highly recommend an IDE controller card for like $20. You simply put it in a PCI slot and the new hdd gets plugged into that. That way you can use the IDE card to read the new hdd and you don;t have to mess with BIOS at all. Works with any computer new or old and it makes setup a snap. Then all you need to do is hook the new hdd up to it and jumper it for a single drive if its by itself on the cable, or master/slave if its with something else.
What kind of hdd is it? Each manufacturer uses different jumper settings.....
Western digital? Maxtor? Segate? ....?
Paul
PS-If you decide to get an IDE controller because of either BIOS limitations or to ease the hassel, I'd recommend this:
http://www.newegg.com/app/ViewProductDesc....-104-214&depa=0