Welcome to Apple Support Communities
First, note that only Mid 2010 15-inch MacBooks Pro and newer ones are compatible with Windows 8. If you have an older computer, you shouldn't install Windows 8 on Boot Camp because it's not officially compatible.
If you have a compatible Mac, download and install the Windows support software for Windows 8 > http://support.apple.com/kb/DL1638?viewlocale=en_US&locale=en_US Decompress the file and run the installer to install the drivers. Then, see if the Magic Mouse works correctly and your MacBook Pro turns off properly