The library is found under C: \Documents and Settings\username\My Documents\My Music\iTunes\ You need to move, or better yet, copy, the "iTunes Music" folder and the "iTunes Library.itl" file to the appropriate folder structure under the new username's folders.
Like copy from C: \Documents and Settings\Stan\My Documents\My Music\iTunes\... to C: \Documents and Settings\Ollie\My Documents\My Music\iTunes\...
If your profiles are on a different drive, of course you'll have to substitute that drive letter...
Clear?