How To Install XP On Unallocated Disk Space

I have a Getac B300 laptop running W7Pro on a single partition. Through a rather bizarre mix of nostalgia and my love for sheer simplicity, I somehow got it into my head that I wanted to run an XP Pro installation on the same machine.

The next station of this (surely flawed ) thought process led me to wonder whether I could do just that with the already existing Windows 7 installation. I got around to shrinking the C: partition, which netted me some 51 gigs of free space that I figured I could use to create a new partition on which to install XPPro. So far, so good.

As you'd expect by now, simply sticking the XP CD into the DVD drive and restarting the machine just won't work: I got the "XP can't see the hard drive" message. So, armed with Google as my friend, I ended up educating myself about how to use nLite to create a copy with integrated iaahci and iastor. Problem is, Having prepared three copies already, after I start the installation sequence and the XP CD installer starts loading files, I'm ending up with the message "the file iastor.sys could not be found," even though I did make sure to include the file that I downloaded from somewhere in the integration process.

So what am I missing here? What am I doing wrong? (I know that the whole concept is "wrong," but there you have it.)

Here are some of the specs of the machine in question:

Getac B300
32-bit W7P SP1
320GB Toshiba MK2555GSX ATA HDD
3GB RAM
ICH8M chipset.