What can I delete from the system drive?

I have a multi drive system, with the C:\ drive being approximately 5 gigs, the D:\ drive being 80 gigs, the E:\ drive being 20 gigs, and the F:\ drive being 15 gigs.  This is due to two drives, the primary being a 40 gig drive, and the second being a 80 gig drive mainly for storage.  The main drive is partitioned in three parts, with the C: intended solely for the OS.  I never install programs to the C: drive.  All programs are installed to the E: drive, but every time I install something, it seems that the c: drive gets more added files. I have a very clean desktop, with shortcuts to storage folders on the D: drive for whatever may end up on my desktop to be stored within. I keep my recycle bin empty, clean out IE history and cache manually often, and go through the C: drive directory via file explorer often and delete what is obviously junk.  My management plan is to frequently back up the C: drive via an image so that I can always recover to within a few weeks if a disaster occurs.  It works great, but the C: drive is too large, and needs paring down.

When I first installed the OS, it was imagable within Norton Ghost to create an image of less than 600 mb that would fit on a CD rom.  However, it has now swelled to over 1.9 gigs, and I don't know what I can do to reduce the size of the drive.  I want to be able to back it up with an image that is of the smallest size possible so I can save the image to a CD.  What can I do to manage the C: partition?  What can I delete?  Is there anything I can do to move things from the C: drive elsewhere?  What system files can I remove?

I have a P4 with 256 mb ram, Windows 2k.  

What else do you need to know?

Kencam