Modify the registry for programming? I dunno if I've misunderstood you but you do not program your computer via the registry
The windows registry is simply a giant file for storing settings at the end of the day, including quite a few under the hood ones you wouldnt normally touch.
The Windows Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems. It contains settings for low-level operating system components and for applications running on the platform that have opted to use the registry. The kernel, device drivers, services, SAM, user interface and third party applications can all make use of the registry. The registry also provides a means to access counters for profiling system performance.
When first introduced with Windows 3.1, the Windows registry's primary purpose was to store configuration information for COM-based components. With the introduction of Windows 95 and Windows NT, its use was extended to tidy up the profusion of per-program INI files that had previously been used to store configuration settings for Windows programs. It is not a requirement for a Windows application to use the Windows Registry—for example, the .NET Framework applications use XML files for configuration, while portable applications usually keep their configuration data within files in the directory/folder where the application executable resides.
^First 2 paragraphs of wikipedia.
Actually that is a good starting point for some light reading.
Microsoft also have this article: http://support.microsoft.com/kb/256986
Links in that article will also take you through to further information.