there is one site called Universal Hint System. They have hints and walkthroughs for tons of games. Downside is you have to pay for the software that allow you to take full advantage of the site, and that I too often got pop-ups installing crap on my pc, but I guess some blockers can handle that. Take a look and see.
EDIT: Sorry, didn't read "video walkthrough" DOH! Ok, sounds cool, but some games are rather complicated and will need a looong movie
