You're starting to set me off course with changing PHP 5.6 to 5.5 (I really asked for an older 5.6 to use the same loader),
but perhaps you can do another test to see if the OS is up for it (I have Win2008r2Ent on hold but I need to install it from scratch to test - prefer to delay it a bit).
Please try to get the final package from this KB, extract on your Windows (2008 and 7) and see if PHP loads Guard Loader properly.Howto:Setting-Up-Apache,-PHP-NTS-and-Guard-7-Loader-on-Windows
You need the runtime anyway, I don't see in your feedback if you ran a repair, or removed and reinstalled the VC runtime which is mentioned in the readme.txt (and the article).
If it does work - its your setup. Feel free to use my custom package, and you can just use the PHP without Apache of course, its a much shorter setup.
If it does not - its your OS, maybe checking the DLL with some dependency walker / looking for libraries will show what is missing / broken.
Let me know any result.