On some customer Windows platform, I had to install XAMPP 1.7.0 because the application I intended to run does not support PHP >=5.3 and 1.7.0 is the last one to ship with 5.2.
It seems that the eAccelerator module does not work because of a mismatch between the version of PHP eAccelerator has been built against and the one actually present in 1.7.0.
I personally don't care, but wanted to let it know, for the track.
Hope it helps someone, someday.