No access to the Windows source code? Well, Microsoft offers the next best thing. Microsoft Detours 2.1 is now available as a free download. According to the Redmond company, as long as the solution is deployed exclusively on 32-bit platforms, and into research, non-commercial, and non-production environments, Detours is up for grabs under a no-fee, click-through license. The download is aimed at developers that feel the full pain of not being able to hook as deep into Windows as they would like to.

With Windows locked up, Microsoft itself admits that instrumenting and extending functionality associated with the platform or with the applications designed to run on top of it is not an easy task.

“Developers can now significantly enhance their product features by taking greater advantage of Windows functionality through Microsoft Detours. Already, more than 50 ISVs have licensed this research project. Detours can be used to intercept 32-bit and 64-bit functions,” revealed Robert Flaming, program manager on the Windows Installer team.

At the same time, Detours spans over x64 and x86 with support for IA64 processors. In the absence of access to the Windows source code, Microsoft is offering what it referred to as a library for instrumenting arbitrary Win32 functions. The company informed that on x86, x64, and IA64 machines, Detours was capable of intercepting Win32 functions and replacing the the in-memory code.

“Use Detours to create an automatic distributed partitioning system within your product. Or, use Detours to create file backups when file delete commands are issued. You can license commercial rights to incorporate and distribute Detours 32-bit and 64-bit functionality in your own product. The Detours package includes utilities, complete documentation of the Detours API, and a transactional model for attaching and detaching Detours,” Flaming added.

Microsoft Detours 2.1 is available for download here.