Two questions about running a custom-made 200 GB external USB hard drive (Seagate hard drive in an Iomega 120 GB external case; formatted in Windows XP using FAT32) in Fedora Core 5:

1) The drive is 200 gigs, but it's only registering as 137. I don't think it's because of FAT32, but one can never be too sure.

2) When I check the properties of the drives, it says that I have nearly 30 gigs worth of stuff. When I actually try to use it, the number shrinks down to 5.9 gigs. The former number is the correct one, if you haven't guessed already.

Oh... and formatting the drive into ext3 is simply not an option at this point. All of my stuff is sitting on my girlfriend's WinXP system five miles away.

137GB? Looks like buggy (more correctly, slightly outdated) external case - what do you think 120GB on it mean... It is one of the magic numbers.
And try running fsck.msdos on it (well, with actual modification disabled). Maybe it's just corrupted - or maybe partition goes across 137GB boundary, so you are out of luck, because some files and some free space is unreachable.

I had a simillar issue with a 300 gig drive, I formated the drive NTFS and added this to my kernel

http://www.linux-ntfs.org/

Also I had to update my XP, olderversions of XP have issue working with the FAT on newer larger drives due to how manufacturers pack on the plates to increase the size.