FYI... SUMMARY
Installing Windows 8 in BIOS mode on a UEFI system may leave you unable to access the BIOS/UEFI/firmware setup utility. DETAILS Apparently, when you install Windows 8, it matters whether you've booted the Win 8 installer via the new UEFI mechanism, or the classic BIOS mechanism.[1] The Win 8 Setup program installs a boot loader to match the firmware type it sees (reasonable). Further, the Windows boot loader for BIOS does not include any UEFI related features (again, makes sense). So If you originally installed Windows 8 via the BIOS mechanism, there is no option for "UEFI Firmware Settings" in the "Troubleshoot" / "Advanced Options" section of the Win 8 boot loader. (Still reasonable. Why would there be options for something you don't have?) The problem arises in that for many of the "Designed for Windows 8" computers, the primary mechanism to get into the firmware setup utility[2] *is* the Windows 8 boot loader. The "Press F13 for BIOS Setup" or whatever thingy is either nearly impossible to time correctly, or omitted outright. So, if you had, say, changed the firmware's boot mode to BIOS so you could boot a third-party rescue utility, and had neglected to change it back to UEFI before reinstalling Windows 8, you will be left with a Windows 8 install that cannot get you into UEFI settings, on a computer that wants you to use Windows 8 to get into UEFI settings. You can't just switch the machine firmware's boot mechanism back to UEFI, because then Windows 8 will not be able to boot (since there is no Win 8 UEFI boot loader installed). (Kind of like switching an ATA controller from "IDE emulation" to "AHCI native" mode.) On this particular computer, I was able to get into firmware setup by unplugging the hard disk drive, thus forcing a boot failure. But I can't just change the firmware boot mode back to UEFI, for the reason noted above. Fortunately, one doesn't need to get into firmware setup very often. But I don't care what Microsoft thinks, a 2 second pause for "Press DEL for BIOS Setup" is much better than "Disconnect the hard drive for BIOS Setup". I suspect this will be more of a problem for home/consumer systems, at least at first. It seems like business systems are more likely to offer additional boot options during POST, even if it slows boot down slightly. I found some third-party comments that suggest backing up the entire Windows install to external media, changing the boot mode, and then doing a restore. Apparently the restore will put the correct boot loader in place, while restoring the rest of the system. I have some hope of finding a better way. I'm hoping it will end up being like changing your disk controller, as long as you do the right rain dance first, you can bring the system over. But I wanted to put the word out, so others know to watch out for this. -- Ben [1] "BIOS mechanism" may be identified as "CSM", "Compatability Support Module", in some UEFI user interfaces. [2] AKA "BIOS setup", "CMOS setup", etc.
