I bought a new WD hard drive at 500 gig capacity for my daughters' computer. I installed it and created a partition of 100 gig for C.
I'm not sure where I screwed up...but I hadn't noticed she had an external hard drive attached to her comp via the usb port.
Somehow, drive letter F is assigned to the new 500 gig HD and letter C is assigned to the external HD. Checking in "my computer" shows F with 100 gig but no designation for the remaining 400 gig.
I tried reassigning the drive letter to the new HD but it doesn't work. Not sure what to do next. I also bought a new legal copy of Windows XP.