Here is a Microsoft article on the issue:
http://support.microsoft.com/kb/321305
since there is another user on the system who does have access, one way would be for that person to logon, go to ControlPanel/UserAccounts and delete the user with the forgotten password, then create a new account, and if you choose to password it, write that down someplace where you remember where you put it.
Welcome to Wednesday Computer Club BLOG, associated with the Wednesday Computer Club at the Dennis Senior Center, Cape Cod MA.
This blog, reachable from our web site,
http://sites.google.com/site/denniscoa/
is a place for less formal musings and references.
Anyone can add a comment. If you want to be able to post to this blog, send an email to denniscoa@verizon.net asking for access.
there are many archived pages with links to interesting or useful sites.