You might also consider using the free VirtualBox VM software. I installed it and have subsequently installed Win7 Home and Ubuntu 11.04 virtual machines. Win7 Home runs quite well on my iMac 24" system.
I had been running XP Pro SP2 as a VM with Fusion 2 but the performance was always slow. Resuming the Win7 VM is much faster than XP with Fusion 2.
I even have used my old HP 4670 scanner via USB into the Win7 VM.
I've successfully installed Windows XP on on a 2011 iMac with an Intel i3 dual core processor. I ignored the the notice that it only worked with Windows 7.
It is important that you have an install disc with Windows XP SP2 or SP3. My original disc had only Windows XP but I was able to slipstream SP2 onto the disc. Boot Camp would not completely install until I had upgraded to SP3. That caused problems as well, as it wouldn't install until I added a registry entry. If you search for XP and SP3 in the forum you should find an explanation on how to do this.
I also had to install Bonjour to get my HP printer working though I still can't get it to scan.
I wanted Windows so I could run QuickBooks 2009 and it seems to work fine except it will not work with Thunderbird to email invoices. I'll be trying another email client.