Note: IceTV and Topfield do NOT support the use of 3rd party drivers. The following is provided for information purposes only. For support please contact the authors of the drivers below (Henry and Aldarin) from their respective web sites, or ask your questions on the Topfield forum.
How to install a Windows 7 64bit USB driver for the Topfield TF5000
1 - Follow the steps here to run the z4t utility to install libusb-winusb http://users.on.net/~henry/antares/z4t.html
2 - Download and run the IceGuide4Topfield version 3.1 setup program http://www.icetv.com.au/cgi-bin/downloads.cgi?op=get_file&number=15
3 - Download Aldarin's Windows 7 64-bit version of Topfield's tfdll.dll http://users.on.net/~henry/antares/tfdll4winusb1_03.zip
4 - Extract, or unzip, the tfdll4winusb1_03.zip file you downloaded in step 3. Then copy the tfdll.dll file.
5 - Go to "C:\Program Files (x86)\IceGuide4Topfield" and replace the existing tfdll.dll with the one you copied in step 4.
6 - Go to "C:\Program Files (x86)\IceGuide4Topfield\Altair" and replace the existing tfdll.dll with the one you copied in step 4. You can skip this step if you do not use Topfield's Altair application.
If you have never setup or used IceGuide4Topfield with your TF5000 before please follow this guide here (but skip step 2 and the 1st part of step 3): http://support.icetv.com.au/entries/20164461-setting-up-icetv-and-topfield-tf5000pvrt-pvrs
For Windows 8 and 8.1 you will also need to read the following to install the driver from step 1 above, as outlined in this UK forum post: http://forum.toppy.org.uk/forum/viewtopic.php?t=20346&sid=14713b298a2aae5877dbbb642b0b7645