Photoshop/Vista issues?

I have an old version of Photoshop (5) running on a Vista operating system.  Recently it ground to a halt, so I uninstalled it and attempted to re-install from the original disk.  The setup panel displayed ok, but Photoshop did not install and the process just stopped with no error or warning.  Is there something I should know? Really need Photoshop back to continue ongoing projects