No. As of now you can only run and use Xcode on Mac computers. Even though you go to the process of waiting 4 hours for it to download, when it is complete you can't do anything with it on a Windows computer.
You can't install XCode or its SDK on the windows. All you can is create a virtual machine, install Mac OS X there and then install XCode and SDK.
They are "compatible" in the sense that many applications that run on Windows XP will run on Windows Vista.
Many applications and games written for or compatible with Windows 98 will run on Windows Vista.
Yes ofcourse, Windows Vista is upgraded version of Windows XP. Obviously it can run Windows XP applications.
Windows Vista
Windows Vista can already run most XP applications, with no need for any additional software.
your computer might not be powerful enough to run vista. but to be honest i hate vista, get windows 7. Are there any applications running?
open CD drive insert windows vista disk and run it
You should buy an upgrade version of Windows Vista however your computer if running XP is likely not to be powerful enough to run windows vista. You should run Microsoft Windows Vista Upgrade Advisor before upgrading as this will show you any problems your computer may have running Vista.
Yes.
Most programs that run on Windows XP will also run on Windows Vista.
Yes, windows vista is already pre-loaded on this computer when you receive it. More specifically, Windows Vista Home Premium edition.