From Laplink Software:
Of the 66 Windows 7 upgrade scenarios detailed by Microsoft, only 14 are supported by Windows. As illustrated in this chart, among the remaining unsupported scenarios are all upgrades from Windows XP - for the many XP users are there, this makes upgrading to Windows 7 a complicated task. That's why we created Windows 7 Upgrade Assistant: it helps you upgrade quickly and easily from any version of Windows (version XP or later) to Windows 7. XP to Windows 7? No problem. Vista Home Premium to Windows 7 Professional? Yep, we do that. How about Vistsa 32-bit to Windows 7 64-bit? Of course! If you are upgrading your PC from XP to Windows 7, you need PCmover Windows 7 Upgrade Assistant.