When we have guests, I log off my Windows and log in on the Guest "account." Unless I know the person very well, that's ALL they see and all they can use, and it's up to me what programs that account even accesses.

Everyone here has their own accounts but I still don't trust the kids when they visit not to find ways round it - that's the trouble - they are quite smart in some ways but don't always have the resposability to go with it....

Other guests are quite free to use my PC. These days, I set up an account for them and delete after the visit.