How do I unlock my Toshiba Portege 3500 Tablet PC at motherboard password

If you want the fast way, then probably you have to rely on a third-party software. Take a try this password recovery software, it should help clear and reset the lost password and bypass the locked computer.

Note: you can do this on your own, no need to send the PC to anybody for any repair because it's dangerous for your private information stored on the computer, best regards.

I have read an article about how to unlock windows password ,maybe you can have a try.
the article tell us 5 ways to recover forgotten/lost password to login to Windows system.no matter what System your are, you can find at least one way to solve your problem.
hope to help you