Disk usage software

[OzzieGT]

Scandisk says 170GB are being used on my hard drive. I can't find 50 of it...Windirstat says that all the files on my drive are only occupying 120GB. Any suggestions on how I can find where this missing 50GB has gone?

e: I am using Win7 Pro if that helps

 

[Barfo]

System restore images?

 

[tomt4535]

Shadow copies may be taking up some space, in addition to system restore

 

[Emulex]

partition?

 

[OzzieGT]

How do I find shadow copies and / or system restore points to clean out? I tried running WinDirStat as administrator but it didn't make a difference.