Is that PS CS4 that you're using? It could be that since it's an old program, it's not going to be optimized for new hardware and Win 10. Maybe even trying little things like running as admin and set the program's compatibility settings to a previous version of Windows (you can find this tab by right clicking on Photoshop.exe and selecting properties/compatibility). Try different suggestions for speeding up PS first. If that isn't working, then let me know and I can try troubleshooting your system CPU settings.