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View Full Version : first attempt to install on external USB drive


overeduc8ed
29th March 2006, 12:58 AM
I would very much prefer XP on an external drive, since I need every last byte of space on my internal drive for my ordinary Mac stuff, and Windows will only be an occasional need. Also, I'd be less likely to suffer downtime should the Windows side go haywire and hose the drive it's on.

I realize the general wisdom is that Windows XP itself cannot be booted off an external drive, even on computers it was intended to run on. However, there is hope. I saw a link to this site on the macrumors.com forums:
http://www.ngine.de/index.jsp?pageid=4176

I managed to create a version of the slipstreamed install CD with these modifications that enable USB. I then partitioned my external drive using Disk Utility... first 20GB as "MS-DOS" (FAT), and the remaining as MacOS X. I copied xom.efi to the MacOS partition, and blessed that copy. My internal HD remained unmodified, with the stock bootloader.

Upon rebooting, I was then able to hold down the option key, and select either the internal or external drive. Selecting the external drive got me the XOM selector. Selecting the Windows boot, with the install CD in the drive, proceeded normally. However, the Windows installer only saw the internal drive, so I aborted.

The ngine.de web site recommends disconnecting the internal drive when using this method -- I wasn't excited about opening up my MacBook, but did it anyway. Per the instructions on ifixit.com, I opened up the case, and unplugged the internal HD connector. It turned out it wasn't at all hard to do this, it's just a lot of screws to keep track of. As far as I can tell, no seals were broken, so as long as you're careful, Cupertino need not know about it.

Rebooted, with the internal drive disconnected, leaving the external drive as the only option. I selected Windows from the XOM selector, and then... nothing. The gray windows logo stayed on the screen, and the CD stopped spinning after a few seconds. After waiting several minutes, I acknowledged defeat. My guess is that XOM itself assumes an internal drive.

So... while this was unsuccessful, I think this should be a sign of hope. I think if XOM can be modified to recognize and pass info on an external drive, the Windows installer should happily oblige.

My next course of action when I get another evening to work on this -- I will back up my internal hard drive, install XOM and WinXP normally onto it (using the USB-enabled install CD I created), then DD it to my external drive. I think I will run into a similar problem, though -- even if I have a valid installation on my external drive, the XOM bootloader will probably still look at the internal drive for Windows. I wonder if the XOM developers can tweak the bootloader so that it passes the drive the bootloader is loaded from to Windows, rather than hardcoding the primary internal drive...

LimeiBook86
29th March 2006, 06:19 AM
Well I'm happy to see someone's tried it! I would be thrilled to be able to use an external drive and not risk anything on my internal drive. Thanks for trying, I'm sure it'll be possible eventually. :D

chrispy
29th March 2006, 08:10 PM
I'd venture to say that this is a problem with XP not knowing anything about EFI. As far as I know the BIOS is where Windows retrieves the information about the harddrives on the computer and the BIOS knows nothing about USB. I'm sure this could be accomplished if the BIOS emulator mapped the USB drive as another IDE drive in some way. This is mostly guess work on my part though ;) I would also love to solely run windows from an external drive.

Tomzo
29th March 2006, 08:57 PM
I would think that many more people would attempt this if they could install the whole thing on an external drive. I am willing to double or triple my initial donation to a new contest to get this done!

Tom

overeduc8ed
30th March 2006, 03:21 AM
My next course of action when I get another evening to work on this -- I will back up my internal hard drive, install XOM and WinXP normally onto it (using the USB-enabled install CD I created), then DD it to my external drive. I think I will run into a similar problem, though -- even if I have a valid installation on my external drive, the XOM bootloader will probably still look at the internal drive for Windows. I wonder if the XOM developers can tweak the bootloader so that it passes the drive the bootloader is loaded from to Windows, rather than hardcoding the primary internal drive...

Okay... tried this, and as I feared, no dice. I can hold down option, get the Mac to load the XOM bootloader from the external drive, but then the bootloader's windows icon turns upside down and it gives up. Selecting a Mac bootup boots from the internal drive rather than the external drive. I think this means that xom hardcodes booting from the internal drive, regardless of where xom.efi itself is located... so it looks like xom.efi needs a little bit of modification.

dylpkls91
5th April 2006, 01:31 AM
Will this work without disconnecting the internal drive?

I would rather not muck around with anything in my system that could become permanently damaged. Would I just have to reinstall OSX on the internal?