CS3 Serial Number/Uninstall Issue

Hi, I have a weird problem.

I use Photoshop CS3. Recently, I needed a new serial number because the product no longer has a means of authenticating the original serial number. I went here:  Activation or connection error when starting CS3 or Acrobat 8 and received my new serial number. I uninstalled my original software, downloaded the new software on the site, and followed the steps to install it.

For some reason, it kept the old serial number, which stayed no matter how many times I restarted the computer or reinstalled the new software. I tried calling Adobe for help, who only recommended I do what I had already done, then put me on hold for two hours. Finally, I tried uninstalling and reinstalling one more time, but the software stopped responding. The "Add or Remove Adobe Creative Suite 3 Design Standard" is sitting in my control panel, and will not let me affect it, either to install or uninstall. This now prevents me from installing any new versions, so I cannot even upgrade now.

I am at my wits' end. Please tell me what I can do to correct this.