how to prevent a program from running in Windows 7

Sometimes the system admin, or parent may not want a particular program
from running on a computer (ie.torrents and other downloading programs)
for obvious security reasons. This little guide will show you how to prevent
a program from running, and will still apply even if the program is uninstalled
and reinstalled
Start -> Run -> typing in regedit Then you want to navigate to
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Next right click on the right handside pane -> choose New->DWORD (32bit) Value and name it DisallowRun -> Once it’s created, double click on it and
change its value to 1 and then hit Ok -> . Now right click on Explorer and
choose New ->Key. Name the key DisallowRun aswell -> Then right click
on the right handside pane and choose New -> String Value
You can now enter any name you like, ie. Block Bittorrent and then double
click on it and in the value data field you want to insert the exe extension.
(You can find the .exe extension by right clicking on the program and going
to properties in all programs)
Finally restart your computer and next time you try to launch the disabled
application you will get an error message