Hi Capau
Well, if you have LW Basic then you will not have to re-register because no regestration is necessary.
If, however, you had Limewire Pro which you have not updated in the 2 years you had your computer then you will have to register again for $18.88.
To save yourself any problems, I suggest you get LW Basic for now and move up to LW Pro later on.
Here is the URL to the official site:
http://www.limewire.com/english/content/download.shtml
UK Bob