German Installer

The available CS5 products can be found via the following links:

CS5 - http://helpx.adobe.com/creative-suite/kb/cs5-product-downloads.html

For the following, you can download the trial version of the software thru the page linked below and then use your current serial number to activate it.

Be sure to follow the steps outlined in the Note: Very Important Instructions section on the download pages at this site and have cookies enabled in your browser or else the download will not work properly.

CS5: http://prodesigntools.com/all-adobe-cs5-direct-download-links.html

As far as the invalid serial number problem goes, you should go thru the following:

Error "The serial number is not valid for this product" | Creative Suite

http://helpx.adobe.com/creative-suite/kb/error-serial-number-valid-product.html

Activation & Deactivation Help

And for what product exactly?

Mylenium