Hi again,
just to share that, after some more (successful) tests, a new XAMPP package with Moodle 2.7dev is available @ http://download.moodle.org/windows (scroll down).
Finally, I've decided to use XAMPP 1.8.2 because it supports more Windows OSs (XAMPP 1.8.3 does not support XP and 2003) and have added the corresponding Opcache version to it as part of the packaging process, so it comes with caching enabled.
I've tested it under Windows 7 (that's the only flavour I've at hand), so it would be really appreciated if you can try it with anything else, from XP to 8.
For more details, problems and feedback, MDLSITE-2936 is the issue covering this.
TIA and ciao
PS: Once we verify it's working ok for we could update current Moodle 2.6 version to use the same, newer and better, XAMPP version.