RampageOC

Hello i have a mad problem i am on the family computer and seem to have downloaded a virus . I downloaded a file on limewire and i downloaded a archive file it said it contained UFC events me and my cousin was looking for anyway when i opened it loads of things opend and now my computer is real slow . Also when i turn my computer on i get the message

An Error has occured while initializing active shield .
Method comcappfactory - register
results -

after results it gives me a code

also when ever i turn the comp on a icon appears on the desktop it is like a pc set up the screen a disk and the tower and it is called

freeprodtb

I delete it and when i turn my comp on it redownloads .

Please any one help . Can i fix it thanks very much for any help you people give