windows 7 - What app can i use to track disk space?

I dont know what is going on but my disk space seems to be going down and i am not downloading anything. What app can i use on windows to keep track of diskspace? I used windirstat which tells you how much data a folder is holding but i still cant figure out the problem.

I did notice a folder holding 1.7gb for visual studio's intellitrack (or whatever that thing is called)

-edit-
Today i found it has taken up 7gb (weird, after deleting i only have 4gb and i can see in windirstat that it says 7gb). My HDD actually hit 0bytes left on the C drive.

C:\ProgramData\Microsoft Visual Studio\10.0\TraceDebugging