Windows 7 Upgrade Advisor - This will check all your hardware and soiftware for compatability:

http://windows.microsoft.com/en-us/windows/downloads/upgrade-advisor

 

Comparison of the various packages :

http://www.microsoft.com/windows/windows-7/compare/default.aspx

 

Compare Windows XP & Vista with Windows 7:

http://www.microsoft.com/windows/windows-7/compare/versions.aspx

 

Advantages of the 64 Bit Operating System:

http://www.microsoft.com/windows/windows-7/features/64-bit-support

 

Methods of Installing Windows 7:

http://windows.microsoft.com/en-us/windows7/Installing-and-reinstalling