MacNN cites two tips they received noting changes made to Boot Camp in Mac OS X 10.6.6. The first suggests that Apple has dropped support for Windows XP. When setting up a Windows partition, Boot Camp requests an "...authentic installation disc of Windows 7 Home Premium, Professional or Ultimate." XP isn't mentioned.
Also, users are discouraged from using software from a Mac OS X install disc or another computer in an attempt to find drivers and the like. Instead, Boot Camp will prompt you to download "additional software designed specifically for each Mac" to get your keyboards, etc. working. Just as MacNN speculates, we agree that this measure is meant to ensure that users have the latest software, helping to eliminate future troubleshooting.