You might have installed a 2nd copy of XP to the F: partition.
Look at what's on your C drive. If you still have the C:\WINDOWS folder, the chances are you have 2 copies of XP, one on C and one on F.
When you boot up the computer, do you get a boot menu, with 2 "Microsoft Windows XP Home/Professional" for you to choose.
Or click Start, Run, type msconfig and press Enter.
Select the Boot.ini tab, and see if you have 2 lines (instead of just one) underneath the section [operating systems]?