i messed up my newer mb (asus tusl2-c) so i switched back to my older mb (pc100) it doesnt have any usb port. is it possible to use my scanner and webcam on it?

It is possible to get a USB to serial converter cable. Though how effective they are I have no idea.

Here is a Google search result for them.
http://www.google.com/search?q=USB+to+Serial+converter+cable&sourceid=opera&num=0&ie=utf-8&oe=utf-8

You can also get a PCI card that will allow you to add USB to a non-usb mobo. I have used this type of card in the past with mixed results.

Here is a Google search result for them.
http://www.google.com/search?q=USB+PCI+card&sourceid=opera&num=0&ie=utf-8&oe=utf-8