"Using icloud PC requires Windows Vista or Windows 7; Outlook 2010 or 2007 is recommended for access to contacts and calendars", says Apple. Yes, Windows XP is not compatible with icloud, which operate on iTunes yet 10.3 and MobileMe.
Apple has always been very conservative with Windows, preserving a great backward compatibility because of the unwavering support of XP users to their OS. If Vista was not convinced things are different with Windows 7, which is gradually forgetting his great ancestor. As does Microsoft itself, moreover, Apple thus moving towards the phasing out of Windows XP, which remains the operating system most widely used.
Remind all intents and purposes that Apple is much more aggressive with its own OS: it has always supported the version of Mac OS X and the current version. Thus, iTunes 10.3 is only compatible with Leopard and Snow Leopard, and it is not surprising that the media is full icloud as Lion and Snow Leopard.
