It's probably not worth the headache, *but*... depending on the adapter, you can sometimes get away with using the same 2.5" -> 3.5" PATA adapter you would use to put a laptop drive in a desktop system, but you must supply the 3.5" drive with outside power (usually from a PC supply).
The best thing to do if you just want to check out the system would be to use a live CD as the other posters suggested. I would suggest Hiren's Boot CD, D***SmallLinux, or Puppy Linux.
MCITP: EDA, MCSE NT, MCSE 2000, A+
Work: Thinkpad T410 / i5-650 / 8GB / 500GB / Win7 Ent x64
Personal: T60 (4:3) / T7200 / 4GB / 500GB / Ubuntu 12.04 <scrap built>
Retired: 570E, T20, T21, T23, T30, T40, T42, T43