If Steam was installed in a non-default directory, your SteamVR config/log paths may be referring to non-existent directories.

To fix your SteamVR installation path:

1. Navigate to: ...Steam/steamapps/common/SteamVR/bin/win64
2. Run vrpathreg and fix the paths to the correct drive and directory, or delete the openvr.vrpath file in user/AppData/Local/openvr

Ensure that hidden files are set to show on your system:

1. Click the Start button > Control Panel > Appearance and Personalization > Folder Options
2. Click the View tab
3. Under Advanced settings, click Show hidden files and folders, then click 'OK'

On Windows 10, do the following to show hidden files/folders:

1. Select the Start button, then choose File Explorer
2. Select the View tab
3. Check the Hidden items check box to view hidden items

1. Launch the Steam client
2. Hover your cursor over the LIBRARY button
3. Select TOOLS
4. Locate and right-click SteamVR in the tools list
5. Select Delete Local Content

Once uninstalled, double-click SteamVR in the tools list to re-install.