In theory, it should work.. if you have
independent installs.
1. Ensure that the install hard drive has only one partition with an NTFS / Fat32 partition id. That partition should be the only one that is formatted as NTFS / FAT32. It should be a primary partition.
2. Install XP.
3. Make a 1:1 copy and store it somewhere safe.
4. Format that same primary partition.
5. Install Vista.
6. Generalise the BCD, so that it will boot from any partition without needing a "repair".
7. Make a 1:1 copy and store it somewhere safe.
8. Restore XP to the first primary partition on the dual boot drive.
9. Create a second
primary partition.
10. Boot into XP. If the second primary partition has a drive letter assigned, go to step 11. Otherwise, go to step 12.
11. Use disk management to remove the drive letter for the second primary partition. XP should now, in theory, ignore the partition.
12. Restore Vista to that second primary partition. Vista should be ignoring the XP partition, by default. Check.
13. Install a third party bootloader, like GRUB.
14. Marvel at working hibernation?
Someone will probably be along shortly with a less convoluted method.
