korrd's freelancer account manager.(sry for not having the link at hand, it's somewere on the site)
Or you could go to your files (unless you wrote it down to begin with) the code you get upon installing FL, every install get's you a different key.
If you still have access to your old computer go to..
Start > programs > microsoft games > freelancer > examine account ID
And either write down the code or print it of.
Then on your new computer the first time you click muliplayer a new code will come up, instead of hitting ok delete the new code and enter the old code then click ok, you should have your old account now.
I'm not able to connect to the server, there are people online but the connexion can't be established. Is the problem from my computer or from the server?