If you wish to copy themes from one Windows 7 system to another, copy the contents of
\Users\Username\AppData\Local\Microsoft\Windows\Themes,
where Username is the account name for the account from which
you wish to copy the themes. If the new system doesn't have a Themes
directory under the
\Users\Username\AppData\Local\Microsoft\Windows\ directory, because no themes have been added, just copy the Themes
directory itself from the source system to the destination system.
Afterwards, on the destination system, you can right-click on an empty area of
the desktop, select Personalize, then select the theme you wish to use.
Note: you may need to turn on the display of hidden files and folders to locate the directory as described here.
