There is a non-techsavvy user, who doesn't want to learn, and can only use Windows XP or 7. The problem is, that the computer is shared which she would like to use, and the computer stores sensitive, important data. Since she clicks on everything, it's quite a russian roulette.

How could I isolate her account from the rest of the system? Like having a profile on the computer (it runs Windows 7 now) which would have the files and other stuff sandboxed?

I was thinking of having a dual boot system, but that could compromise the files too, or the boot sector (talking about Windows). Linux is not a way, hence ... see the first line.

Is there such a software that can set up a sandboxed environment?