Hi Aare,
HTC USB Modem Driver 2.0.6.24 for Windows 7 64-bit 64-bit driver download - X 64-bit Download - x64-bit download - freeware, shareware and software downloads.
Based on the description, it appears that you are having issues with finding a driver for HTC Sync for Windows 8. I will definitely help you with this issue.
1)Do you receive any error message when trying to install the driver?
Method 1: I would suggest you to download and install HTC Sync software from the link and then check if it helps.
Usb Drivers Windows 7
For reference:
Windows 7 Ultimate X64 Drivers
Support - HTC Gratia
Method 2: If the issue persists, I would also suggest you to install the drivers in compatibility mode and check if the issue persists.
Follow the steps to install in Compatibility mode:
a. Right click the driver installation file and select Properties then tap or click the Compatibility tab.
b. Place a check in the Run this program in compatibility mode for: box.
c. Tap or click the drop down box and select a previous operating system, then tap or click OK.
d. Try installing the driver and check.
I hope it helps. If you have any issues regarding Windows in future please let us know. We will be happy to help you.