I've got a 10-yo exchange student bunking at my place for a week, and I've allowed him to use my PC for gaming purposes. He doesn't need to use the net browser, so to prevent him from visiting unnecessary (and potentially harmful) sites, I want to lock my browser. Is there a way to password-protect Firefox? I tried the Master Password solution offered by some users, but it doesn't work. Another alternative is to use an encrypter; I'm currently looking at Axcrypt. Is it safe/good?

As in prevent browsing? You could go with one of the totally web abhorrent services that subvert your DNS. They do free trials, and will happily redirect 'harmful' traffic to a holding page. I think even the 'open' service 'openDNS' offer that.

I'd create a windows user account for him to use, and then use filesystem permissions to forbid him from using anything you don't want him to.

If it is local gaming only, you could just disable the network adapter.

Or even better, get them to agree not to go browsing the web and just keep an eye on them to make sure they don't. Build up a little trust and respect with them :)

EDIT: The latter should require nothing more than deleting browser shortcuts from their account (desktop, start menu, quick launch).

This. It's easy, fast and a 10y old probably can't bypass it.

Well I went ahead and just put a password on the two PCs. Easiest way that way. Besides the kid has to do his homework and I wouldn't want him to be distracted. :X

Still, has anyone used Axcrypt before?

Can't you just rename the program file folder, and maybe a few of the executables (the ones that are obviously Firefox)? That would break the shortcuts and he'd have to know where you hid the files, even though they're in plain sight. When he's gone, just rename those few things back again.