How to prevent application to run on your PC

WinXP Pro
1. Start -> Run -> Type "secpol.msc".
2. Right-click on Software Restriction Policy -> Create New Policies.
3. Right-click on Additional Rules (on the right) - Choose New Path Rule.
4. Now click Browse and find the executable you don't want to run.
5. Make sure the security level is set to "Disallowed" and click OK.

WinXP Home
1. Boot into Safe Mode ([F8]).
2. Login to the Administrator account.
3. Navigate to the executable.
4. Right-click on the executable -> Properties -> Security -> [Advanced].
5. In the Permissions folder, for all users:
6. Edit -> Traverse Folder / Execute File -> Deny -> [OK].
7. Reboot.

Via: http://bit.ly/tDjL