Starting from Windows and installing OSX? AHCI bios changeover might BSOD your Windows install

[khazk]

Just wanted to post this for people who are starting their OSX journey with an already-functional Windows installation and maybe don't have THAT much computer savvy that this solution didn't pop-out quickly.

 

(Background: I installed OSX on a brand new SATA hard drive to avoid the madness that partitions may/may not cause for my first go-round. As such I had to change the SATA mode from IDE to AHCI, which is part of the install requirements for OSX86. My BIOS defaults to IDE mode, so when I installed Windows it was set that way. Note that since I don't have eSATA drives, a RAID setup, or require hot-swapping, I would not have enabled AHCI mode in BIOS prior to this new setup. If you already use/d RAID, or hot-swap eSATA, or other hard-disk related stuff, then you probably had AHCI enabled during your Windows install or some time previously and may not encounter this boot issue. Also, before I found the KB article below, I did a bunch of MBR repair functions, etc. using Recovery Disk and "Repair Startup" options but would still BSOD right after Windows animation played. I was basing this all on searches here saying "set Windows as the active partition" etc. Note that most of the installs here for multi-boot are fresh, specially-partitioned, or begin with a different OS (Linux/OSX first vs. Windows first), so this is a special case that might be considered "well, duh" by more advanced users than me. )

 

Using the BIOS boot device selection (i.e. F12 at startup) I would select the OSX drive and it would load with Chameleon appropriately. Unfortunately doing the BIOS boot device selection for my Windows install was getting the instant BSOD with 0x7B "INACCESSABLE_BOOT_DEVICE" (sic...Microsoft! Spelling!).

 

(NB: Windows doesn't install AHCI support unless it's a fresh install with BIOS already set AHCI as per their KB article 922976: During the Windows 7 or Windows Vista installation process, any unused storage drivers are disabled. This behavior speeds up the operating system's startup process.)

 

So a quick change back to IDE mode to get Windows to boot again and sure enough, it started no problem. I followed the steps as per the KB article http://support.microsoft.com/kb/922976:

 

To resolve this issue yourself, enable the AHCI driver in the registry before you change the SATA mode of the boot drive. To do this, follow these steps:

1. Exit all Windows-based programs.
   
2. Click Start, type regedit in the Start Search box, and then press ENTER.
   
3. If you receive the User Account Control dialog box, click Continue.
   
4. Locate and then click one of the following registry subkeys:
   
   • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
     
   • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV
     

[*]In the right pane, right-click Start in the Name column, and then click Modify.

[*]In the Value data box, type 0, and then click OK.

[*]On the File menu, click Exit to close Registry Editor.

 

(NB: Note that it says "click one of the following"; I had to do it for both keys since they were both set differently than "0".)

 

And rebooted. I then immediately changed the BIOS back to AHCI mode and selected Windows via BIOS boot device selection and crossed fingers. With the registry settings changed, Windows recognized the change in SATA mode and began the "Found New Hardware/Installing Software" process. I got a "You must restart to save changes" and then tried the BIOS boot selection to OSX drive. Went Chameleon boot options and highlighted "System Reserve" partition, hit Enter, and Windows fired up without problems.

 

Hope this helps someone who is wasting way too much time trying to get this to work.