Photoshop 5.5 serial number rejection

When I bought my G3Mac (OS 8.6) I also bought Photoshop 5.5 upgrade (which included ImageReady). ImageReady however has disappeared from my system for some reason and try as I might to reload it from the original CD, I keep getting an error message which says that "this is not a valid Adobe serial number", yet it's the same number which comes with the CD slipcover!
Is it possible to get around this? I would really appreciate a response from a Mac pro as I am out of my depth when it comes to technical problems.
Many thanks,
Regards,
Norman.

Norman,

Where did you buy that upgrade CD?

Call Adobe Customer Service (not tech support) to find out why you get that error message. Use the Contact link at the top of this page.

norman,

I take it this is a recent purchase, and it was cheap. Be aware that with old technology, you will be limited in both the apps that will still run on it and with the degree of support you'll be able to get from any source.

But as Ramón suggests, you may have been given a bum deal on the software...

Neil

Many thanks Ramón and Neil for your replies, I will follow through on your suggestions, much appreciated.
Regards,
Norman.