The `msvcr90.dll` is a Dynamic Link Library (DLL) file associated with the Microsoft Visual C++ 2008 Redistributable Package, which is part of the Microsoft Visual Studio 2008 suite. The "msvcr" prefix stands for Microsoft Visual C Runtime, and the "90" indicates its association with Visual Studio 2008. This DLL contains the C runtime library functions used by C and C++ applications compiled with Visual Studio 2008. These functions cover a wide range of operations, including file manipulation, memory allocation, string operations, mathematical calculations, and other standard library functionalities. The presence of `msvcr90.dll` is essential for the execution of applications developed with Visual Studio 2008, as it provides the necessary runtime support for these applications to run on Windows systems.

The `msvcr90.dll` and other runtime libraries are typically installed on a system as part of the Microsoft Visual C++ Redistributable Package for Visual Studio 2008. This redistributable package ensures that all necessary runtime components are available on the target system, enabling applications that depend on these libraries to function correctly. If users or developers encounter issues with `msvcr90.dll`, such as error messages indicating that the DLL is missing or corrupted, it can lead to problems running applications built with Visual Studio 2008. Resolving such issues often involves reinstalling the Microsoft Visual C++ 2008 Redistributable Package, which should restore the `msvcr90.dll` file and other associated runtime components. It's important to source the redistributable package from official Microsoft channels to ensure system integrity and security.