It is unable to run Window 7 OEM after installing Windows 8 Customer Preview Version on separate HDD.
When installing on a separate HDD (external or internal) Windows 8 Customer Preview Version, the Windows 8 boot menu appears. However, the screen goes blank when choosing Windows 7. The only way out is hard reset of the notebook or PC.
To boot into Windows 7, instead of Windows 8 Customer Preview Version, is to enter boot menu during pc’s boot by pressing F12 (on most notebooks and PC’s) and choosing the hdd on which Windows 7 was installed. If booting without pressing anything, the system will boot into Windows 8 by default unless the boot order in BIOS is changed.