Ok, I'm guessing that being it is a beta, does it specifically say that it is for x64 and still bearing in mind that it is a beta it is not installing untill you reboot, it is still working on the old drivers untill you reboot.
Per their site:
This download is a beta driver providing Microsoft® Windows® Vista 32-bit and 64-bit Beta Build 5231 support for Creative Sound Blaster® X-Fi™. It is not fully tested and provides limited functionality
THIS IS AN UNSUPPORTED BETA DRIVER. There is no technical support for this driver.
* We recommend that only experienced users install this driver. Do not install this driver for critical tasks.
* This download supports Windows Vista 32-bit and 64-bit Beta Build 5231 and may not work on other Vista builds
There has been a mixup at Creative's website and the wrong driver details have been posted. Here is the corrected version:
This download is a beta driver providing Microsoft® Windows® Vista 32-bit and 64-bit Beta 2 Build 5384 and Build 5456 support for Creative Sound Blaster® X-Fi®. It is not fully tested and provides limited functionality
Personally I would go back to what works untill it becomes supported!