Photoshop - Installation Error

Without further information we can't help.

Which operation system do you use? What is the exact error message?

Take a look here

Adobe error "Case-sensitive drives not supported" or similar install error | Mac OS

Your disk is set up wrong. The message says so. If you don’t understand - this is normal - find someone who does; fixing this is a long and dangerous process. Back up carefully, your disk must be wiped.