|You may need to format the unallocated space brfore you can merge.|
Let me suggest something else. Your father evidently partitioned your drive like it is. That is actually good.
You probably don't perform any backups either do you?
How much of the 14GB of files on the C drive are actually OS and program files?
Right click on My Documents and choose the general tab. how much space is being used by My Documents?