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REF:

http://windows.microsoft.com/en-US/windows-vista/Tips-for-finding-files

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QUESTION / PROBLEM

I am running out of diskspace on my hard drive, and have no idea how to find the files that are taking up the most room.

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ANSWER / SOLUTION

In Windows XP, simply right click your C: drive, and select Search.
This will will bring up the Windows Search tool.
Click the ‘Click here to use Search Companion’ link at the bottom of the Windows Search left window pane.
Click ‘All files and folders’ in the ‘What do you want to search for’ dialog
Click ‘What size is it?’, and Specify the ‘At least’ setting you want.
Click the

[Search] button.

In Windows 7, navigate to your C: drive in Windows Explorer
In the Search text box at the upper right side of the Windows Explorer window, type something like
size: >400MB
and hit enter
This will find all files on the C: drive that are greater than 400MB in file size.

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http://www.anysitesupport.com/how-can-i-find-large-files-on-my-hard-drive/