ENat for MSN Messenger makes it possible to talk with anyone using MSN Messenger voice chat or video chat even when behind NATs where attempts to talk using MSN Messenger voice & video chat usually fail. It also enable file transfer when behind NATs. A NAT device usually sits between private network and public network. If your PC has a private IP address, then your PC must be behind a NAT device. Under this situation, MSN Messenger or Windows Messenger usually has trouble when using voice chat, file transfer features. To work around the problem, you may try ENat for MSN Messenger.