File missing... Please reinstall...

My Photoshop CS4 started giving me this error message after a system reinstall (OSX 10.4.11):

''One or more files in the Adobe Application Supprt folder, necessary for running Photoshop, are missing. Please run the Photoshop installer and re-install Photoshop.''

I try to reinstall from disk #1 of the Creative Suite 4, Design Premium set of CDs.

I double-click on the ''Setup.app'' icon and nothing happens.

Wait 5 minutes - still nothing happens!

I purchased this software from Adobe and registered it.

Why won't it work???

There are posts all over the internet about this 'reinstall' problem but I haven't seen posts about the software failing to reinstall.

Please help.

Dan H.