I have a problem unlocking S2, i was in demo few times this week and i cant unock S2...

I need it tonight, can someone help me?

What do you mean "can't unlock"? What message are you getting in LFS?

Unlocks for this week are all used...

can i turn that off?

No. You get 1 more unlock every friday, to a limit of 2 maximum. This is by design to stop account sharing and crackers. If you message the developers directly (using this form http://www.lfs.net/?page=mailus) and explain why you managed to use them all in such a short time, you might get some more unlocks if you're lucky.

To avoid this in the future, you don't need to lock LFS to go back into the DEMO servers. On the Multiplayer screen, before you click "Display list of hosts", you just select "Demo" from the "Online mode select" at the top. To change back to S2 you just select S2.

The only reason you need to lock LFS again, is if you don't want someone using your account online, because they have access to your computer.

Thank you very much

And FYI you don't need to lock lfs just to race on demo.