Osetup.dll is a file that is needed by Microsoft Office to install correctly. It is a DLL file (Dynamic Link Library) that is also used once Office is installed to control plugins and other add-ons that Office uses.
Microsoft Office 2007 uses a lot of DLL files when it's installing and during normal operation. Some are only used rarely, but files such as Osetup.dll are more integral to the Office suite of programs. You may find that Office doesn't run correctly if Osetup.dll is missing or is damaged in some way. You may also find that Office refuses to start. In rare occasions, when Office components are active in other Microsoft programs, you may see error messages even when Office isn't running.
You will most likely see DLL errors relating to osetup.dll if the file is missing or corrupt. Examples of error messages are:
These error messages usually occur when there is an issue with the installation of Microsoft office. Certain viruses have also been known to interfere with this file, and the file can sometimes become corrupt on its own. If the file becomes unstable, it may not register on your system, hence the "file not found" messages.
If you receive a Osetup.dll not found error when trying to install Microsoft Office, or when inserting a Microsoft Office CD in your computer, it may be because the autorun function is not working correctly. In this instance the solution is to manually install Office by browsing to your CD and double-clicking "setup.exe".
If you see error messages at other times, it may be because Osetup.dll is missing or corrupt. To solve the issue, you should try one of the following methods: