Many Debian based distros come with QTParted, a kind of Partition Magic clone, though it doesn't work nearly as well. Look for it in your menu. For this particular job, I think QIParted will do nicely.

If you want to just use the fat32 (vfat) partition for storage of files, you can leave it as is. Linux will be able to read and write to it. If you really want to change it to a linux filesystem, say to expand your home partition, you can do so, as long as Linux is on a logical partition.
 
I agree with Dan, Qtparted will do the job for you either way. It will, however, not touch ntfs partitions.
 
Is your distro on one large partition, or does Ubuntu install on multiple partitions?
 
I'll look at the Ubuntu page later and see what i can find.

To get space for Fedora Core 2, I used the Knoppix cd to run QTparted to shrink the windows partition, you have to defragment the drive first, but that is easy under windows. Then your drive has unused space with no partion on it and when you install Linux it automatically uses this free space (Just make sure you hit "Delete all Linux partitions, there aren't any anyway, and not "delete all partions")

ubuntu does not install qtparted by default but you can install it using apt. Fire up synaptic and find qtparted mark and install it. or from the command line type sudo apt-get install qtparted. Then you can just launch it from the applications menu > System Tools> QTParted or cmd line sudo qtparted
 
you can also use fdisk to recreate that partition. It's all command line but if you are comfortable exploring it it's not that hard.
I'm pretty sure ubuntu creates a / and /home I've always done custom partitions when I set it up. go to the cmd line and type df -h this will show you the parttitions, devies name, and sizes.

Quote:greg@milo:~ $ df -hFilesystem Size Used Avail Use% Mounted on
/dev/hde1 5.6G 1.6G 3.7G 30% /
tmpfs 380M 0 380M 0% /dev/shm
/dev/hde2 50G 36M 47G 1% /home