Microsoft included the Arial typeface (to avoid paying a licensing fee for Helvetica) with the introduction of Windows 3.1. Apple licensed the Helvetica typeface for use within the Mac OS. Helvetica...
Software written for Mac OS X is not compatible with the Windows OS. Apple do make versions of some of their software for Windows such as iTunes and the Safari browser.
Mac OS X is an excellent replacement for Windows 7. You can use Apple's Mac OS X on computers made by Apple. The legal terms you agree to when installing Mac OS X prevent it being installed on...