should be able to goto the Windows XP section of the microsoft site and somewhere there will be a button or link to the windows catalogue, go to it, and then click the hardware tab and go down the side bar till you find laptops, click it and then scroll down the resulting list to find if it is compatible.
Also check the Dell site it should also provide you with information about upgrading and drivers and software.
Read up on your hardware and get the drivers on a CD before hand I really recommend that.