I recently purchased a new PC with Windows 8, and no longer have access to the old one to deactivate Photoshop on it.
I believe the version I was using was CS4, which I couldn't reinstall.
I think my serial number pre-dates the Creative Cloud system and/or my account, so there is no record of the purchase aside from the serial number that doesn't work.
According to the system, my serial number is not eligible for the discounted purchase for owning CS3+.
I know other people have had this problem, and the advice generally consists of 'call customer support', but I cannot get through to an active support line and was told no such support exists for the product and sent me back to this website.
If anyone has an active number to call from Australia that would help, if nobody on the forum helps first that is.