windows - 1Tb Hard drive showing 30Gb remaining

I'm using Windows 7 64 (a Dell i5 box). I have a 1Tb C: drive with the following partitions:

1. 39MB (OEM Partition)


2. 13.15GB NTFS (Recovery partition)


3. 918.32GB NTFS (Boot Partition)

When I "Select All" in Explorer on C: root (with hidden and system files visible) and choose properties, it shows approximately 270GB used in total. However Windows tells me only 30GB of my drive is free. Somewhere I've lost over 600GB.

I did the following:

1. Run chkdsk (everything is OK)


2. Run disk cleanup (recovered around 60GB).

So I'm still down almost half my drive. How can I find out where the missing space is?

Answer

So after much messing about, I managed to find the answer. The trick was to run WinDirStat as Administrator. When you do that the missing files magically appear. In my case they were all in Windows/Temp.

On closer inspection it turns out that a particular installer writes a 3mb log file every time it fails, before trying (and failing) again. I had over 200,000 of these files in Windows/Temp. The cultprit was a program with id {9C593464-7F2F-37B3-89F8-7E894E3B09EA}, which I believe is Visual Studio 2010 or 2013. Repairing VS solves the problem.