Question: Are DLL's (example: run.dll) part of the operating system? If I was to reinstall windows 95 or install 98 will they be replaced. The reason I ask is that I did a virus scan and a lot of the DLL's were infected and erased. Honestly I don't know how the system ran at all with all the infections in there. It was running windows 95.
Answer: Dynamic Link Libraries (DLLs) are used for any section of a program that is not always required or which can be shared between programs. They are loaded dynamically as and when required rather than being statically linked into each program that uses them.
Those DLLs belonging to the operating system will be installed when you (re)install the operating system. Those belonging to application software will be reinstalled if you reinstall the appropriate application (eg. Microsoft Office Suite).
This article written by Stephen Chapman, Felgall Pty Ltd.