I would consider the best way to be one that is the most cost efficient and effective for your goals. The Windows XP to Windows 7 upgrade is not easy, there is barely an upgrade path (less an official one), but it can be done. The third party products, specifically, Ghost migration, may save you a lot of time and headaches, but Microsoft will still recommend an automated, official solution.
While there is no official upgrade path from Windows XP to Windows 7, there is an upgrade path from Windows XP to Windows 8, or Windows XP to Windows Vista, to Windows 7. The third party products may make a Windows XP migration to Windows 7 much more feasible, but this should be brought up with the third party vendor.
Can u explain me about: Windows AIK - Automated Installation Kit?
Do I need to run Sysprep on each machine?
Please help me...
Need to know what is aik,
And another way for updating from xp to 7?
Is sysprep needed?
If I got different type of computer (motherboard, drivers...)
What is the best way to create one image for all type of computers..???
OK. If you do not have the technical training or expertise to do this, you need to try it in a test environment first. Mass deployment requires working knowledge of sysprep and Windows Automated Installation Toolkit. The upgrade path from XP to Windows 7 is also not viable, but a Windows 8 path is. You need to look into this more in the technical articles I posted above, as this may require a great deal of time and organizational cost to your business. It may be such a pain, that if you do not want to use an automated method, you could do it one-by-one manually. In almost every automated instance, this will require your systems to be completely networked with either a Windows Server or master computer to roll out the updates.