Yes it does look like you were scammed. Pity it's too late to cancel the transaction thru your bank/credit co. See This about the story. And see if you can recognise the site your purchased your LW from the list of scam sites here.

I would recommend you delete the program you have now & any traces of it. Then downld the free version from here http://www.limewire.com/english/content/download.shtml

Start with the free version & if you like it then consider LW Pro. LW Pro does improve performance but not drastically.

See some hints on LW use here: To continue files downlding (click on link) which has links to other valuable skills & tips. And also see this: Tip: Purge the Downloads Queue!
Other tips to reduce drag on your system are:
* After opening LW wait 10 to 20 mins or longer before using. Let it settle down 1st.
* Go to LW's prefs>Speed & tick disable Ultrapeer Cap. & press apply button.
* Set both uplds & downlds to autoclear.
* Reduce uplds to about 70-80% or more.
* Reduce downlds to 80 or 90%.
* Don't use the Resume button on all incomplete files. This can have side-fx such as affect LW's connection quality. May queue your files for much much longer. This will also stress LW & your comp. If you use Resume/Find sources then just apply it to a couple or so at one time.