When you ask a question you need to provide some basic information
-Forum quick start https://forums.adobe.com/docs/DOC-5601
Mac or Windows, and EXACTLY which version of the operating system?
Recent Mac AND Windows operating systems have been known to cause "odd" problems
Are you using a computer Administrator account with full read/write permission?
Exactly which version of the program do you have that is causing problems?
Do you have an OLD program and a NEW operating system?
For Mac
CS6 and earlier programs have not been tested and will not be updated for Mac El Capitan/Sierra
-which means that you try to use CS6 and earlier at YOUR risk of having problems due to Apple updates
-Apple did not maintain backward compatibility with old programs in El Capitan or Sierra
--Adobe has a workaround to Apple's problem of not maintaining backward compatibility
--help links and Adobe solution to Apple's problem in this message https://forums.adobe.com/thread/2301916
For Windows
Two ideas that MAY work to install and/or run old programs in Windows 10
-RIGHT click the program icon or EXE and select a compatibility mode in the pop up option window
-or Run as Administrator http://forums.adobe.com/thread/969395 to assign FULL Windows permissions may help... says Encore, but sometimes required for ALL Adobe programs (this is NOT the same as using an Administrator account)