Notes about the BC! file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The BC! file type is primarily associated with 'BitComet' by BitComet.com. BitComet is a p2p file-sharing program fully compatible with Bittorrent. The .BC! extension is an incomplete download and you should not try to open this file. This also applies to BitLord. When the download is complete the .BC! extension should change to whatever the correct file extension should be for the complete download.