Bad news -- it sounds like you've been caught out by some savvy scammers.
The site you have given money to is part of a group of scam sites that seeks to charge for a service that is otherwise free. This particular one provides "access" to Gnutella, a peer-to-peer (P2P) file-sharing program similar to Napster, LimeWire and BearShare. You can download it for free from multiple legitimate places, including CNET.com.au's Downloads section.
Basically, this scam site advertises "music downloads", but what they actually offer is the ability to download a file-sharing program that will allow you to search for audio files in other people's shared libraries. You have paid for something that you could have gotten for free, and any music you download will be obtained illegally.
Many of these sites appear legitimate, offering customer support and advertising on Google. However, you should be wary of any service that claims to offer unlimited music downloads for a one-off fee.
A site called p2pscams.info has established a list of known music scammers, or "rogue sites". If you're searching for a legitimate music download service, some local options are the iTunes store, NineMSN music, and sites partnered with Destra Music, such as For further information see .