sorting out a mess--- partitioning and dual booting.

I have WinXP already installed and decided to add Ubuntu 9.1, and dual boot. Problem was, during the installation process, after I'd partitioned my hard drive, I had to interrupt the process and re install. Once I got Ubuntu up and running I downloaded Gparted to try to "clean up" what happened. I'd like to figure out which of the partitions are being presently used for ubuntu, and which ones I can delete or resize, and how to do it without losing crucial data. At present I'm afraid I'm a bit too much of a newbie to do this on the fly, so caution prevails. Any advice appreciated... thanks.