can I end a tournament early?

I'm only a free member right now, and am finishing up a really long tournament with a group of 12 people.  I have only 3 games left, and two are very close to completion.  Yet some people have at least 15 games left to play!  Once I am done with my games, can I "leave" the tournement in order to play in another one (since I can only be in 1 at a time), or do I have to stick around waiting for the other games to finish?

Basically, can I withdraw, and still win because I've finished all my games?

You can finish tournament by press Withdraw. This will resign only  games in progress. But this tournament will stay in My Current Tournaments

I free member and now i have 2 finished tournament in My Current Tournaments.

I try join to other tournament ant it is posiible.

I try join to once more tournament and receive message:

You are currently playing in 1 tournament.
If you would like to play in more tournaments, upgrade your account now!.

So, if you withdraw one tournamet then you can join any other tournament immediatly.

I think once you've played all your games you're free to join other tourno's. But I might be wrong...

Or, you could sign up for a different membership.  Its well worth the little cost involved if you play chess fairly often.

But if I'm doing very well in the tournament, can I withdraw and still win?  Or if it is a multi-stage tournamnt (it's not, but I have also been wondering about this) is there any way for me to play in another tournament also but still move onto the next round?

Don't withdraw. Just join another once all your games are done. Find out if the bug was fixed.