what I would like to accomplish on my home PC is something similar to what my account at my University's computers does. I would like to have an account with almost no privileges. The only things I want the account to be allowed is to use already installed software, temporarily save stuff on the computer, but in a manner that every changes made by the user will be discarded after reboot unless it's in a specified folder which would be the only folder where the user would really be allowed to save and keep data on (for example in My Documents) and that's it. Everything else I want him to only have read access for.
If someone could explain to me how I can do that I would be so grateful, and if it could be explained for Windows 7 I would prefer, but XP or Vista will also do.