Sitas suveike man

NOTE: This applies to Windows 7. Only minor differences exist for other 
Windows versions.
Close all applications
Go to Control Panel -> Region and Language
On Formats tab, set Format to English (United States) (don't change anything 
else)
On Location tab set Current location to United States
On Administrative tab in the Language for non-Unicode programs section, 
click the Change system locale button and in the new window again select 
English (United States)
Click OK and restart Windows when prompted

After that, start Steam again and execute Verify the integrity of game cache 
option one more time (right-click game in your Library, select Properties, 
go to Local files tab and click the said button).

Start the demo and it should work.