You can change drive letters very easily, and provided your XP install is on
an active bootable partition you can change the drive letter by the following:
Goto "My Computer">Control Panel>Administrative Tools>Computer Management>
There you will see a tree table of options, goto Disk Management.
From there you can re-assign your Hard Drive letters, CD/DVD drive letters,
Zip drive letters and Labels as well if you wish.
Of course if your XP installation isn't on the active bootable partition
it's very likely you'll have to start from scratch again.
I used to be able to use a bootdisk with the FDISK utility on in the past,
this still might be a valid option to make your F:\ Drive the active
bootable partition, then re letter it and label it later, but it was so long
ago since I last did that, I'm not sure if that will work with NTFS?
Having said this, my earlier suggestion should enable you to charge the
drive letter of your Zip Drive to one other than C:\
I hope this is of any use to you?