administrator has set policies to prevent installation

Hello. I am using WIN 7 64bit home premium. Some older games will not run after installation (Battle stations pacific). I have been told that uprading windows and running in xp mode can fix older games not running. I also have a game that will not install, 'Napoleon total war' (uses steam) when I get a message 'the administrator has set policies to prevent installation', this game should install on win 7 according to the system requirments. I have read through many forums and found no solution that will fix this on my pc. All the fixes I have read about are not possible or don't work. Steam installs fine from the internet. Bad company 2 runs fine.
1> Tried switchng UAC off, same message.
2> Same massage when run as administrator.
3> Tried (Start, Run, rsop.msc) 'windows cannot find this please check you have typed correctly'.
4> Local security settings do not exist.
5> Tried this, 'Browse the registry to HKLM\Software\Policies\Microsoft\Windows\Installer
Create: DisableMSI Type: REG_DWORD value = 0 (0 should allow you to install it was originally 1)'. Along that path there is not 'Installer' within 'Windows'.
6> Tried 'Browse to HKEY_CLASSES_ROOT\Installer\Products\
Search the list for the product that is causing the error.. delete the folder in the products folder… this may also correct your error…'. This did not work.
7> All drivers are up to date as far as I am aware and windows is updated.
I am at a complete loss, whoever can solve this for me I will be internally greatful to.
Regards, Ben.