Change disk used for offline files in Windows 7

"To change the location of the offline files cache (by default it's in %windir%\CSC)

Disable Offline files
Open regedit, navigate to

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CSC\Parameters

create a new string value called CacheLocation and set it to the desired path, for example:

\??\e:\csc

Note: you have to use the Windows NT format for the path (backslash, double question marks, backslash)
Reboot, then re-enable Offline files (which in turn will require a second reboot)

If you want to keep the cache contents the process is a bit more complicated:

How to move the client-side caching (CSC) folder to a new location

As a final note, if you somehow manage to mess up the CSC cache (which isn't very difficult, I did that several times...), and Offline files start behaving strangely, you can reset it to a clean, empty state:

Create a new DWORD value FormatDatabase = 1 in the above mentioned registry key and reboot."