John H. wrote:
I have a 160 GB external hard disk to which I tried to back up my documents
and settings using the Windows backup system.

After about a half hour, I get a message saying there's not enough room for
the backup, and that if the hard disk is FAT 32, the backup can be no
larger than 4 GB. So I checked, and sure enough, the external HD is FAT 32.

Now what? I already have about 50 GB of stuff on the external HD that I
don't want to lose by reformatting (if that's what's required).

Forget about windows backup utilities and get Retrospect.