I use WinGuard Pro 2004 Free Edition. It allows me to lock any windows programs, any of my files or folders and also block web page content. In addition it can block people installing software and downloading from the internet. This is great in helping prevent viruses, as if people can't download and install software, then the viruses can't get onto your computer, that way at least! It also has the option to block popup windows and so much more. Becuase it comes in a free edition I seriously recommend it. It stops kids and adults messing around with your PC settings and your personal files and so much more.
See http://www.winguardpro.com for more info and free download.

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