The most prevalent symptom for an operating system (or systems) that are installed in IDE mode (in some BIOS firmware implementations otherwise called 'Combined IDE mode'), is that the system drive typically fails to boot, with an ensuing error message, if the SATA controller (in BIOS) is inadvertently switched to AHCI mode after OS installation. In Microsoft Windows the symptom is a boot loop which begins with a Blue Screen error, if not rectified - and through no fault of Microsoft Windows.