Can Photoshop CC 20 17 only be installed on drive C?

No, it can also be installed on other hard disks.

The method is as follows:

1. Open Adobe Creative Cloud, find the Settings button in the upper right corner, and click Preferences.

2. Look for Creative Cloud in preferences.

3. Find the application below, and then click the installation location below to change its installation location.

4. Click the file, and after confirming the change of location, you can click Install Software.

5. After the installation is completed, you can move the mouse to the software location, right click, select the location to open the file, and view the folder where the file is installed.