Time Machine - I don't want to reformat

[DJMastaWes]

Hey guys! So, here are to pictures:

I have like, 93GBs in use on my MacBook Pro, and 172 available on my external hard drive, but it says that I need to reformat the external.
Most of the stuff on the external are things that aren't on my computer, that I can't get rid of.

I'm wondering if there's a way to use Time Machine, without erasing/reformatting my external hard drive, because I have the space, so I don't see why I need to.

Thanks for the help guys!

 

[Nugget]

Is your Lacie drive formatted HFS+ or is it formatted FAT32 (so you can use the drive on Windows machines)? I suspect it's FAT32, which is why Time Machine reports that it needs a re-format. Time Machine requires an HFS+ formatted partition.

You might have some luck resizing the FAT32 partition (not sure what tools exist to do this in OS X, but if you've got a Windows machine handy it wouldn't be too hard). Then you could make a new HFS+ partition in the remaining space available on the Lacie drive.