GHOST backup and restore on small HDD

(Preface- I did search through the forum and didn't see this particular problem listed).  I've got a legacy machine with a 5 Gb drive (!) and I'd like to make darned sure I back this up.  I have a handful of 5 and 10 Gb drives to use.  I back up to a remote machine over the network.  The images, when I double click, show all the files that I expect.  The problem is, when I go to restore and select either the 5Gb or 10Gb drives as the destination, I get an error message saying that the destination isn't big enough.  The image files are 1Gb in size.  When I try to just restore to a 'modern' large drive it apparently will go through OK, i.e. no error message at this point.  I tried this with the small drives formatted FAT32 and unformatted.  Neither works.  Any ideas would be GREATLY appreciated.