I realize you probably already bought and installed a drive, but, to help anyone else, I just replaced the original HDD (it crashed) in my HP Pavilion ze 5170 with a HITACHI Travelstar 5K100 HTS541010G9AT00 (13G1591) 100GB 5400 RPM ATA-6 Notebook Hard Drive from newegg.com for $70 shipped. It's quieter, faster, and larger than the original 40GB drive and so far it works great.
Side note: when I was using the recovery discs to install the WinXP and drivers (and all the other crap that comes on them) I got a "PXE-E61 Media Test Failure". To fix this I just changed my boot order to read my CD-ROM drive first and the install when swimmingly.