64 bit compatibility

If we forget about the SATA drive for a moment, if the XP install was not made on that system, it will give a BSOD when it boots because the IDE drivers will be the wrong ones. Unless the IDE drivers baked into the XP install are EXACTLY the right ones for the mobo, OR the generic Microsoft IDE drivers are in use, XP will give a BSOD every time it boots.

IF the XP drive would boot all by itself on the system, then you could go into BIOS and disable whatever hard drive you don't want to boot from, and (in theory) that would work.

To create a true dual-boot system you would need to use a third-party boot manager, such as easyBCD or DualBoot Pro.

It's tricky to do without a utility since Windows install programs like to act like they are the only OS on the computer.

http://www.howtogeek.com/howto/8790/dual-boot-your-pre-installed-windows-7-computer-with-xp/

There are Hardware Issues to consider.

The Big one is that the Hardware Sets it's Defaults long before the Software comes into Play and Hardware [b]Always[/b] sets IDE Drives to Primary Boot Device.

As you already have a SATA Drive installed just fitting a IDE Drive should prevent the machine from Booting into the OS Loaded on the SATA Drive as the primary Boot Files on the Root of the SATA Drive will not be found as the Hardware looks at the IDE Drive for these files when the IDE Drive is connected.

After you fit any IDE Drive you'll have to do a Repair Install of both OS's again so that you can get them to work and then if you decide to remove/replace the IDE Drive at a latter date you'll be back in the same boat with a nonworking system.

To do a Repair Install of XP you'll need a M$ Branded Install Disc not a System Makers Recovery Disc and then follow Method 2 here

http://support.microsoft.com/kb/978788

Similar Steps will be required for 7.

While some System Makers Recovery Disc's may allow you to do a Repair Install most will not so if this is an Out of the Box System you'll most likely need new install Media as well. ;)

Col