Getting rid of the partition D would lose you 16.26GB. You cannot rid partition C as it has XP on it?
3.88GBis a little small for C with XP, programs, all those files on it.
I would start over, wipe the drive free and then when you install XP set up your partitons (if you want 2 or more).
Or...just format D and install everything on to that.