I have found that the Windows 7 drivers work on Windows 8 but the HTC Driver installer will not allow a windows 8 install for some reason. There are 2 ways to do it but this is the easiest as I have already pulled the full driver pack from a Windows 7 driver install to make it easier for everyone.
Instructions to installing HTC Drivers on Windows8 64Bit:
1. Download the Windows7 (64 Bit) drivers here - http://d-h.st/OYI
2. Unzip to any location you want. Just remember where you put them.
3. Plug in your phone to your USB cable.
4. Open your Device Manager (Windows Key + X and select Device manager) and locate HTC under Other Devices and right click on it and select Update Driver Software
5. Select "Browse my computer for driver software"
6. Click Browse and then select the folder you unzipped with the drivers in it then click next.
7. It should now install your drivers and then in your device manager it will now show up "My HTC" under Android USB Devices.
Hope that helps anyone having troubles getting USB/HTC drivers working on Windows 8 (64bit).
Now you can use adb and fastboot commands. I use Fastboot Commander and I can report it works perfect in Win8.
EDIT: Im sure this will work for any other HTC phone as well as I am pretty sure the drivers are pretty universal for HTC phones, just so happens I have an Evo3D and do not have any other HTC phones to test this on other then my Hero. I will test that as soon as I can to see if that works also and update my findings.