Nero is software for burning CDs/DVDs, but you can get nero attachments (according to DH)
legally yes you will have to buy it, says Dh, but you might be able to find it online to download if you know where to look (bittorrent maybe?)
He also says that if you might be able to reinstall it from your original disc, but you'd have to wipe it off your PC first and 'clear the registry' That means naff all to me I'm afraid, but maybe it rings a bell with you.