Select Start, All Programs, Accessories, System Tools, right click on Disk CleanUp, click Run as Administrator. Scroll down the drop down menu and you should see the Windows Update Cleanup option. Check the box before that option.
Select Start, All Programs, Accessories, System Tools, Disk CleanUp to empty your Recycle Bin, remove Temporary Internet Files and other selected options. I also recommend you click on the More Options tab, System Restore and remove all but the latest System Restore point. Run Disk Defragmenter.
To investigate disk space usage download, install and run Treesize (freeware) as Administrator.
http://www.jam-software.com/treesize\_free/
Place a shortcut to Treesize on your Desktop, right click the icon and select Run as Administrator to open Treesize. You need to run as Administrator to see all files. If you cannot see the contents of the System Volume Information folder you have not run Treesize as Administrator.
Information on Treesize
http://www.jam-software.com/treesize\_free/
When you open Treesize select Scan from the Menu and you will see a list of drives. Click on C and it will generate a list of Folders. Post the names and the sizes of the 6 largest folders and the total at the top of the list.
Change Default Installation Directory in Windows 7 & Vista
http://www.intowindows.com/change-default-installation-directory-in-windows-7-vista/
How to Change the Default Location of Windows 7 User
http://www.sevenforums.com/tutorials/18629-user-folders-change-default-location.html