This is not OS related.. but I would think, hardware support. Bootcamp 4.0 (version that comes with Lion) does not Windows XP or Vista. Only Windows 7 is supported by Apple. Even the Apple support site doesn't work, as I tried to overwrite the Bootcamp 4.0 with 3.1. ,, I got an error in Windows stating "Bootcamp requires 3.1 or later" kind of a, confusing. Why would you wanna run Windows XP on late 2011 based Macs ? Well, games for starter, or applications that can't be fooled by windows 7 compatibility mode. Even XP mode wouldn't do the job as that still virtual.. like running Parallels. Thanks allot Apple. You just my life more difficult. This could also be a good reason to keep your older Mac as well. I guess there is no way around this apart from installing Windows 7 ?