(temporarily) uninstalling Linux

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[EDIT]
Hold off on any advice, I found a Microsoft guide that I'm going to try out and I don't want anybody to spend their valuble time helping me if I can fix the problem on my own.
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Apparently I need to whipe Linux off my hard drive before I can install Windows XP. I can't believe it, but I don't know how to format this hard drive!

Here's what I did:
I made a DOS boot disk (floppy).
I booted to it and typed the command "format C: /s" and it said C: is an invalid directory! :^(

I have no idea why it would give me this error or what else I can try. Is this because it's a SATA hard drive?

In short, how do I format this hard drive so I can install Windows XP (and then Linux)?

 

For some reason I can't edit my last post.

Anyway, I got these instructions from Microsoft and tried them. The instructions are weird, because the Fdisk utility actually works nothing like they describe (you always enter numbers to make the program respond, pressing "p" or any other letter that the guide says will actually do nothing at all).

But I still used the fdisk utility to delete both partitions it recognized on my disk (it said it deleted them). Then I rebooted my computer, and Linux started up as usual. Nothing had changed. Then I rebooted and ran fdisk again, it recognized the same two partitions it did last time. So I deleted them. It said there were no more partitions on the disk. I rebooted, and Linux works just fine.

So how do I uninstall Linux?

 

I formatted the hard drive using the Fedora Core 5 install disc then hit Ctrl+Alt+Del as soon as it started installing files. But I still can't install Windows and when I boot to my hard drive, something called Grub opens.

So now I guess I need to know how to COMPLETELY uninstall Linux.