Hi, thanks for the post. I suggest you first try the following steps regarding the issue:
1. Click Start, go to Start Search.
2. Type regedit and press Enter.
3. Locate the entry: HKLM\Software\Policies\Microsoft\Windows\Installer
4. Then, please check if DisableMSI is set to 0, if so, please change it to 1.
5. Please restart the computer and check the result.
Meanwhile, you can also check the following thread for related solutions:
The system administrator has set policies to prevent this installation
http://social.technet.microsoft.com/Forums/en-US/itprovistasecurity/thread/6c62e6cc-7893-421d-8b90-8e14eaa1eb48/
Hope this helps!
Sean Zhu - MSFT