I'm not sure how...
Even if you weren't using 64bit, there still is
NO WAVEDRIVER for Vista, 32bit or 64bit.
You need the wavedriver for Winamp. It is just
not physically possible that you could have been running Winamp through the MBox 2 on Vista anything, let alone 64bit, as there is no driver AT ALL for it under Vista.
The only way you are going to get Winamp to work under Vista
anything is to use the ASIO plugin for Winamp.
Now, about the ASIO driver and using it with FLStudio; you might want to try the solution rom
this support page.