Hey again. Yes, you can run SteamVR titles without the Vive software being installed. The issue you're seeing here is related to SteamVR, not Viveport (which is what you're trying to install).
Error 108 is usually an issue with USB drivers. This is SteamVR's troubleshooting page which details some steps to take. Here's their troubleshooting steps:
This error may be a USB driver issue. Please try the following troubleshooting steps:
Reboot your headset:
Right click on the headset icon in SteamVR.
Select Reboot Vive Headset, and wait while the reboot process completes.
Power cycle your Link Box:
Unplug the Power and USB cords from the PC side of the Link Box (not the orange side).
Wait a few seconds, then plug the Power and USB cords back into the Link Box. You may see more drivers install. Wait for this process to finish.
Repeat steps if needed
Restart your computer (Quit Steam VR before shutting down your PC)
Plug your Link Box into a different USB port on your PC:
Try plugging your Link Box into a USB 2.0 port, as some USB 3.0 and 3.1 chipsets can cause issues.
You can also try a USB port that's already in-use and working - move the other device to another port and plug in your Link Box.
If this problem persists, try resetting your USB devices.
To be clear also - Fallout 4 is not the same game as Fallout 4 VR. If you haven't yet redeemed the code that came in your box, you'll need to do that, get the Fallout 4 VR code, and redeem it in Steam. Here are some details on how to redeem your in-box code.
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