You can not login with EPiServer CMS Login page on Windows XP because you get an error "This operation requires IIS integrated pipeline mode".
This is caused by adding the following to OnLoad():
Hi and thanks for the bug report.
This is a known issue, and has already been fixed. The bug actually existes in less than one day, but managed to creep it's way into the build you're testing.
Per GunsarfsEPiServer development team