While MSDN is a bit impractical to browse (there's simply so much stuff in there) it's usually the best place to go to for documentation when doing Windows dev.
The magic numbers (hashes and UUIDs) sort of make sense because there's a slightly adversarial interaction between developers and Microsoft. If you just had a compatibleWindowsMin and compatibleWindowsMax field with version numbers, people would just go ahead and put "9999" in the max field, and then OS upgrades break applications again. By using UUIDs instead, an application developer can't intentionally or unintentionally declare compatibility with unreleased Windows versions.
While MSDN is a bit impractical to browse (there's simply so much stuff in there) it's usually the best place to go to for documentation when doing Windows dev.