Filetopia is a centralized file swapping tool for Win32 which also has powerful Instant Messaging capabilities. All data transfers are encrypted, and using something called bouncers (users who act as proxy servers), can be anonymized. Filetopia has powerful file catalog features which allow you to quickly compare your files with someone else's and see what you're missing. Future versions are going to include meta-searchability similar to Napster's. Could become the closed-source, proprietary, centralized counterpart to FreeNet.