Definitely a Mac is the right choice
Source: I'm using a MacBook Pro right now
No, Microsoft ActiveX controls cannot run on Mac OS X.
Microsoft Office 2008 for Mac is created by Microsoft for Apple's Mac computers and it requires Mac OS X to work. A Dell is not an Apple Mac and is not running Mac OS X and so Office 2008 for Mac will not work.
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No, the Registry is a feature of Microsoft Windows only. Neither the original Mac OS or the newer Mac OS X have ever used a Registry, Mac OS X is based on Unix which has never used a Registry.
operating environments
Linux Ubuntu and Apple Mac OS
Yes.
Microsoft Office for Mac is available for download from the Microsoft website. (see related link)
It will depend what you are trying to achieve and how you define better. If software is written to use Microsoft's Windows system and is not available for Apple's Mac OS then Windows would be better. If you are using a Mac made by Apple then the Mac OS would probably be more suitable but you can always switch to Windows on a Mac if needed. If you are looking for a cheaper, virus free, trouble free computing experience then Mac OS would be your choice.
Yes, it can, if it has Mac OS X running
Macs use an operating system called Mac OS X which will not run applications written for the Windows operating system. Microsoft produce a Mac OS X version of Word for Apple's Mac computers. There is the option of installing the Windows operating system on a MacBook alongside Mac OS X which allows Windows applications as well as Mac OS X applications to be used.
The Microsoft Office suite for Macs is usable on a Mac computer running Mac OS X. The specific requirements for the current version are: Mac OS X 10.5.8 or later RAM 1 GB Hard Disc 2.5 GB