Without the version of Windows that it came with and NOT the version that is reported on screen but what's on your Windows CD I have to recommend you stay with less than 127GB hard disks.
Newegg.com and geeks.com have plenty around for not much.
I have a 7 yr. old Dell Dimension 4500 home computer that needs a hard drive upgrade. It seems to take forever for it to load up in the morning when we first turn it on. It came originally with a Pentium 4, 2.0 GHz processor.
Can anyone give me a reasonably priced recommendation on what to replace this old one with?