ah, wait. if it's returning '/', then that's perfect.
i assumed xarServerGetBaseURI() is the problem, but obviously it isn't.
then it must be embedUri = 'E:/xaraya/html/index.php?module=gallery2'.
in xargallery2helper.class around line 819:
// get the name of the xaraya entry point file (usually index.php)
$scriptName = preg_replace('|/([^/]+/)*|', '', $_SERVER['PATH_TRANSLATED']);
obviously PATH_TRANSLATED returns a wrong value in your case. or not what i expect. i acknowledge that perhaps i should check more than just PATH_TRANSLATED. but for the lack of development time at the moment, please just fix your system manually by replacing this line with
$scriptName = 'index.php';