How to boot Windows XP on a Mac from an external drive?
If you install rEFIt it will give you a boot option menu on every boot in which you can select any partition or external device to boot from.
I wanted the multi-tool of USB drives. Two partitions: one bootable Mac partition and one that could be read from and written to by both Macs and Windows machines. I finally got it done and I don't know why it works, but it does. Here's the deal:
Equipment needed:
- A 16GB USB drive or larger (try to find one that is fast too)
- A drive or partition with a minimal OS X build of your liking (10.6.7 for me was 7.2GB)
- A running Mac
- A Windows (virtual) machine - I used Parallels 5 with Windows 7
The procedure:
Partition the USB drive with GUID partition table; the first partition should be FAT32 (or exFAT), the second should be HFS+ (8GB minimum to fit OS X)
Plug the drive into the Windows machine and agree to it formatting the drive (200MB only for some reason) and label it something odd (I use xxx)
Plug the drive into a Mac, fire up Disk Utility, click on the USB drive, select partition tab, select the xxx partition and press the "delete" key. You are now back to having two partitions.
Restore (using Disk Utility) your prebuilt minimal OS X to the HFS+ partition.
I like to do a Disk Utility repair on the HFS+ partition following the restore.
You now have a Mac-bootable USB drive that has a Windows partition which is readable and writeable by both OS X and Windows.