Sorry, i confused with your reply.There is no Mac operating system like OS 10 4.3, if it is 10.4.3, then its Mac OS X 10.4 Tiger.
BTW, You can install Microsoft Windows with the help of Virtual Machine applications like Parallels/VMWare Fusion etc or BootcampBootCamp
It means that installing windows on Mac directly by partitioning the Hard Disk and the Microsoft Windows can only access by restarting Mac OS. See the picture below about how you can access Windows and Mac
By Parallels OR VMWare
If you installed Windows on your Mac using the Parallels or VMware etc then you can load Windows just by opening the application and run Windows from it. With Parallels you can run Windows and Mac OS at the same time. So you have your Microsoft Windows and AOL on one side and Mac OS X on other side. See a sample picture below;
BootCamp is from Apple and its free. But Parallels or VMWare Fusion etc are third party applications and they are not free. You have to buy them, the price shown in their websites are $79
Also you have to buy the Windows OS. You can buy Windows XP, Windows Vista (i won't buy Vista)
or Windows 7.
Let me know what you think...