If it hasn't been changed then it should be stored in:
C:\Documents and Settings\Username\My Documents\My Music\iTunes\iTunes Music\ (where Username is your logon user).

If you don't care about preserving your metadata (play counts, ratings, etc) then just copying the content of that folder onto the new computer inthe same location will let iTunes discover it all on the new box. If you do there is a guide to the extra steps required here:
hifiblog.com/past/2006/05/11/howto-move-your-itunes-music-while-preserving-library-data-when-you-dont-let-itunes-manage-your-music-library/
(bill, Wed 10 Mar 2010, 1:57, 1 reply, 16 years ago)

Thanks Bill.
Looks a bit complicated but I'll give it a go.
( girlinthehole, Wed 10 Mar 2010, 8:31, Reply)