Also I am using Win 7 Home edition, But i want to upgrade to Win 8 Ultimate edition. Is it possible? If yes, then how to do it?
As far as I know, the only retail x86 versions of Windows 8 are "Windows 8" and "Windows 8 Pro". From what I read, everything but Windows 7 Enterprise can be upgraded to Windows 8 Pro, so you should be alright. I didn't try that myself though.
What I did try was an in-place upgrade from Windows 7 Professional to Windows 8 Pro on two machines and that went quite well.