Problem launching HL/CS; And another problem

1. Don't remember when it started and what happened.
When i am trying to start counter-strike, an error occurs: Counter-strike launcher error, half-life launcher error. And cs shuts down. I found a solution how to walk around this problem. I simply need to delete config.cfg before i launch cs. But i would like to solve this problem.
2. Don't know what causes this. When i'm playing cs (or any other game), sometimes it just hangs (stops or whatever, don't know the proper word in English). Then i must press ALT+TAB twice (once to switch to desktop, and second time to go back to cs) and it takes about 10-15 secs to get back in game. But usually i am already dead. Due to that my keyboard suffers a lot. After some alt+tabs the PC hangs itself, and needs to be reseted. Which sucks even more. It would be likely to be some problem with monitor frequency or something, because my game and desktop frequencys differ. But this shit happens even when i'm playing flash games f.e. on miniclip!

maybe there`s smth wrong with your registry , try deleting all keys that start with steam/hl/valve, then reinstall steam.

Even formating didn't help.
I think it has to be something with video card (or hard drive maybe, didn't check it yet). Because i checked everything else already.