Monitor the HDD free space just like the Task Manager does for memory and CPU.
I did it just for playing with windows APIs, but I found it very useful to learn about other applications hard disk usage: Useful to understand why your hard disk is always full!

License:	Freeware
Version:	0.27
Installation required:	No
RAM usage:	about 1244K
Archive size:	21K
HDD used:	49K
Systems:	Win98 - WinME - Win2000 - WinXP - Vista - Windows 7
Screenshoot:
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