Please, Please, Please HELP!!!!

someone give me some security advice about downloading MP3 files from LIMEWIRE. I'm a downloading novice and have had to have my hard drive cleaned and all software reinstalled 3 times because i keep downloading corrupted files and it slows my computer up to a snails pace. It's also costing me a lot of time and money
I have NORTON ANTIVIRUS and additional spyware with a firewall but i still keep getting corrupted files when downloading .Forgive my ignorance if i'm asking a really stupid question, but is there anyway of recognising a corrupted file prior to downloading it .

PLEASE HELP downloading WIZARDS . I surely can't be the only person to have experinced this dilema

Please, Please, Please HELP !!!!!!!!