if he just buys a mem stick with say 16 Gb space on it , copied that amount of files over, then deleted the files on c drive.
he would see if c drive, was really full.
very cheap, test. an no date lost
Ps His given very little information, so trouble shooting is a bit hard.
I won't give any more pointers, as he run he gob off at me.
most would have just laughed at the joke.