I think either they do not provide any support for the older sound card or someone has forget to put up the link to the driver. However after some googling for the filename, the location of the driver file is revealed.

Here is the installation guide for Genius FM801:

1. Download the driver file in self-extract compressed exe format.
2. The driver installer will then prompt you for a path to extract. Select a folder.
3. After extract the driver setup files, find setup.exe and execute it.
4. Genius SM-Live series PCI Audio Setup program will start and you just need to follow on screen instruction to continue the setup.
5. Restart your PC to finish the driver setup for Genius FM801 AU.

The driver is a WDM type and will install the following devices to your Windows:

1. Genius SM-Live Series PCI Audio (WDM)
2. Genius SM-Live Series PCI Joystick Controller
3. Genius SM-Live Series Mixer
4. Genius SM-Live Series MPU-401
5. Genius SM-Live Series FM Synthesizer
6. Microsoft GS Wavetable SW Synth

I am not sure of thie Genius FM801 AU driver will work for Windows Vista as there is no mention of Vista driver support for this model. You can try it out yourself if you want.

Alternatively, you can try the Free Driver Scanner.