How do I get my Photoshop Software to work on a new hard drive?

[Bahiri]

I have a licensed download of Photoshop I bought from ebay, which worked with the serial key on my old hard drive, but now doesn't accept the serial on my new hard drive after re-installing XP. Is there a way to find the serial key on my old hard drive (which I still have and can connect to my current working PC) and transfer it to my current hard drive? Not the biggest whiz on computers but hope this explanation is clear. Thanks.

Overall Screened Cables

[m3clutch]

you are supposed to deactivate your serial from the program on your last computer so that the serial will "re-work" with photoshop on your new computer when you punch in the serial again.