There is a service tag on the bottom of the laptop. You can go to Dell.com using that service tag and get all the specs on that laptop including its maximum memory.This will indicate whether you can upgrade the memory.

Computer Arabia in Doha can easily upgrade the memory if it is physically possible.

The best way to reinstate XP is to use the recovery CD that comes with the computer. It may be possible to get that recovery CD off Dell's web site if you do not already have it.

Hope this helps
Wayne Hann