Microsoft Office Web Components 11.0 (OWC11) is a legacy library primarily used with Office 2003 for embedding interactive spreadsheets, charts, and pivot tables in web pages or desktop applications Microsoft Support Official Download and Status Download Availability

msowc.dll: Found in C:\Program Files\Microsoft Office\Office11.

Important Warning: OWC is Obsolete & Unsupported

Do not use this in new projects.
Microsoft Office Web Components (version 11.0, often referred to as "OWC11" or "110") was discontinued around 2007. It is:

Spreadsheet Control: Enables viewing and basic editing of Excel-like spreadsheets within a browser.

Part 5: Modern Alternatives (Should You Even Use OWC 11.0?)

This question is vital. While this article focuses on how to download and make OWC 11.0 work, you must ask yourself: Should you?