Windows 7 - Temp Internet files folder is 118GB full, but no files???

Hello.
I hope that someone can help me with my problem. I a lower-intermediate on a computer.

I have my tower pc on constant all day- to record a streaming IP Camera from my work.
Initially, I saved these files into my docutments- which they would save as .avi files, and after every several days I would delete them as they would take up ALOT of space on my pc.

My pc is 250GB in size, and usually it would be about 80GB full before I had the IP Camera.

Just recently, I noticed all of the IP Camera avi files seemed to have disappeared from my documents if I went directly to the folder... BUT I could still see them in documents when I was choosing a location to save the recordings.
Upon right-clicking the avi files in the latter, the files would be of no size and wouldn't play.

Now my computer is 210GB full in the matter of a week.

After a while of fiddling about trying to find if the files were 'hidden' or somewhere else, and my techy friend had a look as well, we have found that it is the 'Temporary Internet Files' folder that is 118GB in size, but when I open the folder, there is Nothing in there.

Please help!!!

Cleaning up temp. files is no problem. Use this for starters.
Disk Cleanup : Extended
Ccleaner is another little program that can do that. I recommend not using the registry part of Ccleaner. TFC bYy Old Timer is another good little program that works for such things. After your temps are clean reboot.
What would bother me the most is how did these files get put some where I didn't put them. I would run from the cmd. prompt/admin sfc /scannow. If System File Checker finds problems run it 3 times booting after each time.
What security do you have on your computer and have you run scans?
Please fill in your System Specs.