Windows XP Home C and D drives

Need some help please.

My Computer shows two partitions, C local disk (106GB/17GB free) and D local disk (4.95GB/ 48MB free). Can I change the allocations to add some of C's free space to D's total size? I'm assuming there is one physical drive in the box with C and D logical partitions. Windows help offers the option to create or reformat partitions but I cannot find anything on simply moving some of the allocation from C to D. Any thoughts on this? Any way to do this through Windows? Again, I'm assuming it's one physical drive.

I have done the cleanup, deleted temp files and defraged on C and D.
Another odd thing, when I expand or explore D, I see only a 'Recovery' folder which right click properties shows only 212KB !! and 4 files. There is also a 1KB !! user file. I have done my best to unhinder my explorer 'View' options, like unchecking hidden and such, but I cannot display those almost five GB on D. Maybe Compaq really locks down this D drive so I cant mess it up. I'm afraid with just 48MB free on D, it's a matter of time before the system tries to write something there (such as a restore point?), and I could potentailly be screwed.

Compaq Presario, Windows XP Home, 2.5 ghz Intel P4, 512MB DDR SDRAM

It runs like a champ, again I'm concerned about that D drive going to 100% full while I cant seem to explore or alter anything on it, or to simply increse it's partition size.

Thanks for any help/education on this. Jim