Just like many other people, I'd recommend Linux; Ubuntu if you're looking for a good operating system other then Windows.
Hi There You can test drive Ubuntu within Windows WITHOUT damaging your current data or partition. Check out Wubi Works in 98, 2000, XP and Vista Regards
If you opt for Mac OS X then it only runs on Apple-made computers. You cant assemble your own Mac system with off-the-shelf from-the-market parts. Strange that nobody is crying foul or monopoly just as they did for Microsoft bundling IE with Windows.
This is not entirely true. Since the shift from PPC to Intel chips, OS X has been running on "off-the-shelf from-the-market" PCs. It just needs some tinkering around to get it to work, but it's not that hard if you've already been installing Linux. I even know that a personal friend of mine has successfully upgraded/installed to Snow Leopard (and several versions before that) on a PC using only parts bought from the local vendor. As to legal issues and license, I'm sure this is illegal. That's his problem. I'm happy with Kubuntu.
As new member, I am learning a lot of advice/recommendation on best alternative OS to Windows. This is very best forum indeed! Kind regards....
Ubuntu is the best alternative, see their website http://www.ubuntu.com and for help check http://ubuntuforums.org. User friendly, big community, can use your own theme, customize it etc