I just upgrade to win8.1 from win8 and I can\'t start wamp server (2.2 x64)
Try checking that the Apache and MySQL services are still registered as services.
Look in Windows Services for services called - 'wampapache' and wampmysql'
Or if you have WAMPServer 64bit wampapache64
and wampmysqld64
If they dont exist do the following:-
wampmanager -> MySQL -> Service -> Install Service
wampmanager -> Apache -> Service -> Install Service
Then try to restart all services.