Ok.
If you install the 3.3Beta1 or above, you can install the WinXP64 driver.

[Available model]

<ATSC>
- FusionHDTV3 Gold
- FusionHDTV3 Gold-Q
- FusionHDTV3 Silver Plus
- FusionHDTV3 Gold-T
- FusionHDTV5 Gold
- FusionHDTV5 Silver
- FusionHDTV5 USB

<DVB-T>
- FusionHDTV DVB-T
- FusionHDTV DVB-T PLUS
- FusionHDTV DVB-T HYBRID
- FusionHDTV DVB-T DUAL DIGITAL
- FusionHDTV DVB-T USB

[Not available model]

<ATSC>
- FusionHDTV1
- FusionHDTV2
- FusionHDTV3 Silver
- FusionHDTV3 SilverT
- FusionHDTV5 Lite

<DVB-T>
FusionHDTV DVB-T Lite

If you want to remove the 64bit driver, remove the installed driver from  the control panel - add or remove programs.