On startup - "Can't find ARMA2:OA serial number in registry" (Steam version)

[Boriz]

Good day!
I have this serious problem with ARMA2: OA, BAF and PMC. After clicking on Play from Steam's Library I get this error twice in a row:
"Can't find ARMA2:OA serial number in registry. "

Then I get this error:
"No entry 'bin\config.bin/CfgInGameUI/MPTable.shadow'."

Sometimes I get error like this one:
"failed to install application correctly."

Then the game starts but immediately quits with this error:
"Error compiling pixel shader PSSpecularAlpha:0"

This happens everytime I start these games and I never managed them to work. The only game that I can play without any problems is ARMA 2 which runs smoothly on highest details. I already tried to reinstall them multiple times and used verified game's files without any change.

I think the first error is the main issue but I don't know how to solve any of these. Could somebody please help me to fix these problems?

[.kju [PvPscene]]

Make sure to launch steam and the game with admin permission (run as admin).

[Boriz]

Thank you! It works!

I had only time to try OA which works without any problems (so far). I think the rest of the DLCs should work fine.

[.kju [PvPscene]]

Good to hear :)