My C Drive is full when it should not be, what to do?

[Madmaxneo]

First off I know the title is probably misleading but I am no amature (illiterate american spelling).
I am running win 7 64 bit
My C drive is my OS drive and is a 120 gig SSD
It might be:
Recently I purchased win 8.1 pro on the windows site (for my new gaming build) and had problems downloading the file to create a DVD ISO so I contacted MS support (which may have been my first mistake). I allowed them to remote connect to my desktop (which may have been my second mistake) and the tech ran through a whole bunch of things that I had already checked except to try downloading it through IE, which actually worked. But in the process she started the installation for 8.1 on my current rig and may have downloaded somethings that didn't get deleted. This old rig is going to stay windows 7 for now. When it was trying to create the disc I got an error saying there was not enough disk space. I checked and was unpleasantly surprised to find I only had 268 mb left on my C drive when there should be about 21 gigs. I started asking her questions about the things she downloaded and she explained that everything she downloaded would automatically get deleted except for the small install programs in "My downloads" (which is on my F drive). I proved her wrong later after I disconnected but more on that below......
I have WinDirStat and have run it but don't see any problems except there is this "unknown file" that is like 13 gigs. I can't get any info on it as it is not associated with any folders or anything of the like (Virus?). It isn't my pagefile.sys or hiberfil.sys as those are easy to identify. In WinDirStat it is colored yellow and is listed as one big file at 12.6 gigs (the largest file on my C drive). I also ran CCleaner and there was not much to clean up. I just ran WinDirStat again and it is still there at 12.6 gigs. I did some cleanup on the C drive for some programs that I simply had not got around to uninstalling and I was able to free up 12 gigs. I also did a "size:gigantic" search on my C drive and there wasn't much that showed up except for a decrypt file that is loaded up by windows when downloading something from their store and it was 2.9 gigs! Which is the file associated with the download the MS tech started as I figured out after doing a internet search. I deleted it because it was said it is unimportant after making the disc. Which I restarted the download and was able to make the 8.1 pro disc after all that. But that decrypt file is back (after my 2nd download). The weird thing is the "size:gigantic" search did not find that 12.6 gig file that WinDirStat reported.
One other odd thing is I did a properties check on all my C drive files and after adding them up I should have about 30 gigs or so free. But when I check the amount left on C it only says 14.9 gigs now. I will be running a deep virus scan tonight and have scheduled a disc check for the next restart which will be tomorrow morning.


1. What is that unknown file of 14.6 gigs (or how do I figure out what it is)?
2. Are there any other places that windows may put things from a download (a failed disc write at that) other than the temp folder (which I checked and deleted everything that could be deleted)?

3. Any other things I can do?

Bruce

 

[ignatzatsonic]

TreeSize Free - Quickly Scan Directory Sizes and Find Space Hogs

You might try Tree Size Free from the above link. It might give you a more understandable version of what's eating up the space.

Have you checked the space devoted to System Restore points?

 

[Madmaxneo]

I have never done a system restore set up.