Adobe Design Std CS5 serial not valid

no, if you saw an invalid serial number you either made an error when entering the number OR you have the wrong installer.  details:

assuming you're using a valid adobe serial number (6 groups of 4 numbers), you have a mismatch between your installation file and serial number. ie, you can have a valid serial number, but if it's for program A and your installation file is for program B, you will see an invalid serial number message.

common mismatches are language/region (eg, serial number is for western europe and installation file is eastern europe), platform (eg, serial number is for a mac and installation file is win), license type (eg, education vs enterprise vs individual). and one of the most common is using a program installation file with a suite's serial number. eg, using a cs6 suite serial number with a photoshop cs6 installation file. that won't work even though photoshop is included in that suite.

you must use the (correct) suite's installation file (and you can choose to only install one program from the suite). here's official info about that error, http://helpx.adobe.com/creative-suite/kb/error-serial-number-valid-product.html

What error message do you see?

Two ideas that MAY work to install and/or run old programs in Windows 10 or Windows 11
-RIGHT click the program icon or EXE and select a compatibility mode in the pop up option window
-and/or select Run as Administrator to assign FULL Windows permissions
-also https://helpx.adobe.com/x-productkb/global/create-local-administrator-account-windows.html