SDB:Booting Multiple Windows Installations from One Hard Disk
How to boot multiple Windows installations on one hard disk with the boot manager GRUB.
In case you have several Windows installation on one hard disk, the primary partition of the Windows you want to boot must be visible and active and all other primary partitions must be hidden. This can be done with the commands hide and unhide. To do this, open the file /boot/grub/menu.lst with an editor of your choice (as root). An entry for the Windows partition that was visible during the installation already exists in the menu file. For example, the entry in the file could look as follows:
title windows root (hd0,0) makeactive chainloader +1
This operating system is located in the first partition of the first hard disk of the computer (root (hd0,0)). More information on the designations is provided in the article SDB:The Boot Manager Grub
Insert the hide/unhide entries as shown in the example below and add entries for additional Windows installations. The result could look as follows:
title windows hide (hd0,1) unhide (hd0,0) root (hd0,0) makeactive chainloader +1
title windows_2 hide (hd0,0) unhide (hd0,1) root (hd0,1) makeactive chainloader +1
In this example, the first partition is made visible and active when the operating system it contains is booted. At the same time, the second partition is hidden. If the operating system in the second partition is selected, the procedure is the other way round.
Save the file menu.lst to make the changes effective.
SDB:Booting Windows from the Second HD