I upgraded from CS3 to CS5 in December 2013. I have the original discs for CS3, but the upgrade was via a download. I need to reload windows on my PC and therefore Photoshop. Can anyone tell me how to get the download again?

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

You can also 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