P2P File sharing is a great resource of sharing information but on other hand they are biggest threat to your computers. You accidently downloading the virus infected files or could end up downloading a copyrighted software.
Microsoft has a brief article on how to defend against the risks. Check the below link for more information:
These softwares should never be allowed in any corporate environment. These softwares may compromise on your security and could leave your entire network vulnerable to attacks.
You may block the exe running of some Known P2P softwares through software restriction group policy in Windows 2003. There are different ways to block the P2P File Sharing softwares. There are different softwares available to throttle the bandwidth consumption by P2P softwares and give priority to HTTP Traffic. One of those is www.netequalizer.com
For internal P2P file sharing within the company use Microsoft Groove. Check www.microsoft.com/groove. Its a solution for File sharing in MNCs who need to share files among users. Another enterprize solution for centerlized repository of documents is MIcrosoft SharePoint Server. Check www.microsoft.com/sharepoint
Hope that will help you understand P2P risks 🙂
Inderjeet 