Demo not working

[Gniarf]

-Download&install PAINKILLER singleplayer demo, see if it works.
-Disable all antiviruses&firewalls&security junkwares, we never know what those could misunderstand.
-In the nvidia control pannel, did you happen to force some settings (like antialiasing or anisotropic filtering, etc...)? If so, try restoring default settings.
-Did you disable the page file? (madness with 1gb ram only, yet...)
-Just in case: you're sure your DirectX is up to date?
-Last I can think of atm: corrupt setup.exe (unlikely though)