All you need to do is boot into Windows 10 normally, then perform the Windows 10 Compatibility procedure... At least that's what I did.
1. Right click on Photoshop (desktop icon or c:\program files (x86)\adobe\photoshop 6.0\photoshp.exe) and select Properties.
2. Select the Compatibility tab.
3. Check the box marked "Run this program in compatibility mode for:".
4. Select "Windows 98 / Windows Me" from the drop down.
5. Click OK.
Photoshop 6 should now run without any error message.