Multi User Logon Access To Certain Files Programs

setting up more than one user logon for windows xp home edition w/ sp2 installed (using fat32). What I would like to acheive (if possible) is to limit my teenagers (2) access to certain files and programs. More specifically programs such as windows explorer (including right-click on START button), access to the "RUN" command, control panel, and other system controlling programs. I have searched on C-Net and microsoft, finding bits and peices but not all together in 1 post and not a step by step. I am not afraid to edit the registry.Also I do not want to convert this comp to ntfs (unless there is a way to back up a massive amount of data without a cd/dvd burner, as I am under the impression that a re-install of XP and reformatting of hard drive is required to switch to ntfs). What would be ideal (and maybe easier to do?) would be to have teenage-user1 and teenage-user2 logon bring up only a desktop with no taskbar and/or START button, thus allowing only access to the programs that I shortcut to the desktop (this thought just occurred to me while typing this).

These children are 15 and 16 and are smart enough to type a google search for password/registry/command prompt hacks and crackers and such. I haven't seen anything in regaurds to what I am looking for all on 1 system or complete in 1 post/step-by-step. Possibly I am not typing the correct search words, but seems alot of text for a search ( am not typing "the" "and" etc. and am using/trying as many buzzwords as I can think of...) and I get no way too much irrelavent and sometimes confusing info or no matches at all. I may be making a mountain out of a mole hill with how I want to do this, as it probably has been done before, if so a link(s) would be much appreciated as would any advice from "seasoned/in-the-know" users/programmers.