im in win2k but i believe its the same in XP.
START -> SETTINGS -> CONTROL PANEL -> ADMINISTRATIVE TOOLS -> COMPUTER MANAGEMENT -> DISK MANAGEMENT
right click on the C: drive, change drive letter to G: for now.
right click on the F: drive, change drive letter to C:
you should be able to remove partitions and join partitions from the DISK MANAGEMENT as long as its not the system partition. you might want your data on another partition too when you do this so you dont lose it. i think you can join partitions together and not lose any data...not sure though.