is there an application what can allow me to setup a password protection to prevent users from installing random programs to my computer?
Just setup an administrator account on windows and make a guest or public user as well. Users can access installed programs, but are prompted for admin credentials when trying to install a new program. This also doesn't interfere with saving files. So guests for example, can open a word processor and save docs without the need for a password. Users can also download files, just not install them.
Hit the windows forums for more info about setting up an administrator account. It's in all there, you just needed someone to point you in the right direction.