Some do work some don't. Only way to know is to try and see if it works..fortunately most do as iam using smc wireless xp drivers.
If you have XP drivers working on Vista/7 x64, they'd have to be XP x64 drivers. 32 bit drivers will not work on x64! Two things to keep in mind: Software as part of the driver install can be 32 bit, its only the hardware access layer that has to be 64 bit. The driver control panel for your display driver for example doesn't have to be 64 bit at all since its just a settings programme that changes settings in the registry, which any programme can do. There are also INF drivers, such that it doesn't provide the driver itself but just lets Windows know how to use its internal driver! (and provide a name for the driver). Most firewalls and antiviruses are 32 bit under x64, its only the access layer (or whatever it is called) that needs to be 64 bit, which usually ends up being a single driver file thats a couple of hundred kb's). You may be able to use a built in x64 driver, or a driver from the windows update catalog that is similar to your scanner and modify it yourself. The Windows update catalog does provide drivers for some very old hardware so you may be in luck! Sure, if you have the 32 bit code you can modify it and then compile it to 64 bit!