Restrict download/install programs windows 7 home

I support the computers at my Church. I have a problem with users installing programs that frequently end up causing problems. unfortunately written restrictions have not worked. I need a way to restrict most users from downloading and or installing programs. They should go through the Administrator. unfortunately due to financial consideration I have limitations. Does any one have any idea how to do this within the confines of windows 7 home premium or utilizing a economical utility?

Remember Group Policies are not available.

thanks in advance for any and all help.

Frank

As the users are able to install software I will assume they are using an admin account. Only an admin account can install software. All admin accounts are equal and trying to impose restrictions on what they can do is an exercise in futility. The only way to prevent users from installing software is to give them standard user accounts.