Hey OspreyO, when you say that you have created a new partition (which you had installed Windows XP on), is this on the same hard drive where you have Vista installed or is it a completely separate hard drive? (If it is then do the below)
I think in the long run you will be better of wiping Windows XP and deleting the partition that you have created for it especially since you had created an FAT32 instead of a NTFS partition.
First of all insert your Vista DVD into your DVD drive and enter the Vista installation. Hit next from the start screen and then Install Now. Don’t type in your product key and untick "Automatically activate Windows when I’m online", then hit "Next", and "No" when asked whether you want to enter the key. When prompted to choose the edition of Vista you’re installing you can actually select any of them as you’re not doing a Vista install at this point. Also tick "I have selected the edition of Windows that I purchased and hit "Next". Accept the license terms and hit "Next" again, then choose a Custom installation.
Now the next screen that appears should resemble something very similar to this:
You will however should see Disk 0 Partition 1 along with Disk 0 Partition
2. (Since you had already created a second partition when you wanted to install Windows XP).
Click on Disk 0 Partition 2 and then go to the "Drive options (advanced)" and this will bring up an extra 4 options, "New", "Format", "Delete" and "Extend". Click on the format option. (This will wipe the partirion clean [Deleting your Windows XP installation]). Once you have done that Click on Disk 0 Partition 1 and click on the "Drive options (advanced)" once again. Click on the Extend option and press Ok. This will merge the second partition into the first one.
Now once you have done that you will be left with a single partition with Windows Vista installed. You now need to create the partition again (A Fresh one), so to do this press SHIFT + F10. This is a Windows PE 2.0 shortcut to open up a command window. (Very handy) Once the command window has popped up type in DISKPART and press Enter. This opens the Microsoft DiskPart application. You need to select the active disk, so type in:
list disk
The primary disk is generally Disk 0, so type in:
select disk 0
Now we need a list of volumes on this disk, so type in:
list volume
In this case Volume 0 is the one we want, so type in:
select volume 0
Now type in:
shrink
This command will now make a partition around half the size of the whole hard disk drive. Now type:
EXIT
and
EXIT (again)
To quit the command window and get back to the install screen. Click Refresh and the partition window will update – you should now see the original Primary partition plus a brand new partition. Now click on the new partition (Disk 0 Partition 2) and click Format. Once that is done, this is where you now install Windows XP. Eject the DVD, restart the machine (just hit the reset button) and boot off the Windows XP CD.
When the Windows XP setup reaches the point where you're prompted where it is to be installed, you'll see that while XP can see the space we created earlier, it can also see the partition with Vista on it. You should be able to see the space you reclaimed on the disk earlier which has become "unallocated space". Create a second partition using the Windows XP installer screen above by selecting the free space on the drive and pressing "C" to create a partition (if prompted, choose
NTFS as the file system.) Just let Windpws XP install as normal. (Their's no need to do anything differently)
When the system reboots it won't bring up a boot menu. Although XP recognises the Vista partition it doesn't recognise Vista itself. The Windows XP bootloader gets installed to the MBR and Vista can no longer boot.
Because you can't use the Windows XP bootloader to boot Vista, we have to reinstate Vista's bootloader to the MBR and configure it to manage both operating systems. So boot from the Vista DVD and on the screen where you're prompted to "Install now", select "Repair your computer".
The next screen searches for local Vista installations – there should only be one, so click Next.
This loads the System Recovery Options screen. Select the first option – Startup Repair. This looks for problems which would prevent Vista from loading (like a missing bootloader) and automatically fixes them. Click Close and then Finish, and the system will restart and boot into Vista.
Now we need to enable dualbooting with XP, and EasyBCD is the best application to achieve this.
Download and install EasyBCD
Launch the app and go to Add/Remove Entries. Under "Add an Entry" and under the Windows tab and select in the Version drop-down list "Windows NT/2k/XP/2k3". Change the Drive to E:\ and the name to "Windows XP", then click "Add Entry" and "Save".
Reboot the system and you’ll have two entries in the Vista bootloader, and can boot into either operating system.
Hope that helps.
