I'm not sure I understand why you want to partition your hard drive.
Since you are using Win XP and I will presume that this was a factory instal you probably have NTFS as your filing system
Do not fdisk unless you are ready to lose everything on your hard drive.
XP has a built in abilty to partition, although on a 40 gig drive its hardly worth it.
For windows systems go to your controll panel hopefully you have the classic view set up and not the XP view click on the icon "Administrative Tools ---> Computer Management----->Disk Management------> Action ----> All Tasks -----> Change drive letter , partition and follow the bouncing so to speak
and yes partiction magic does work very nicely
never know my limits until I exceed them