Hopefully you could find a specification for you model at the Dell website or failing that you may have to find out from their service what the largest size hard drive you can install for your notebook bios.

Most notebooks today can install 30-80gb hard drives with no problem but if you have a Pentium 2 that is quite old so the bios may limit you to a maximum GB size.

If you are upgrading, get at least a 5400 rpm hard drive if possible (versus 4200rpm) as they are much much faster and you will notice that nearly all desktops have 5400 or 7200rpm hard drives already