Download to Adobe CS5 Web Premium

if you're using @Manan Joshi 's link at prodesigntools.com 

follow the directions (esp, step 1)

save the install file. it won't remain online.

thank jim @ prodesigntools.com

Log-in to your Adobe online account below. 

https://account.adobe.com/products

Assuming you have an older OS to support legacy CS5 and you registered your software at purchase, a download link should appear there along with your serial number.  

If you did not previously purchase it, you can't use it. You will need to buy a subscription to Creative Cloud.

https://www.adobe.com/creativecloud/plans.html

Hi @defaultzqyrcodsmdm1,
Only the latest two versions of the Creative Cloud apps are supported and available for download. You can try and download the older versions of the apps from the following website. If the links mentioned on the website don't work, then it means that Adobe has discontinued providing the download and genuine installers are not available anymore. Be circumspect if someone contacts you claiming to provide an installer in such a case.

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

-Manan