Sometimes uninstalling a program will remove it's associated .dll files, sometimes not. Sometimes the .dll files are shared with other applications. It's never a good idea to just delete a .dll file(if that's what you have in mind).
You can research all the .dll files, find their associated applications, verify the application is still valid, then you can delete the file.
Too much trouble for me as my Win-XP PC has 7,930 .dll files.
I thought operating system DLL files were sometimes linked to other programs and if a DLL file is deleted, it would delete the shared operating system DLL file.
Is it safe to remove DLL files?