I have windows 7 installed on a single hard drive. Can I install windows xp on the same drive by just making a new partition on the drive (say 25 gb?)
I never did it on the same HDD, I had a spare drive that I added it to so that I could dual boot - but I can't imagine why it isn't doable. http://www.howtogeek.com/howto/8790/dual-boot-your-pre-installed-windows-7-computer-with-xp/
Not at this point. With windows o/s, you have to install from the oldest first to the newest. The reason for that is that M$ o/s always make sure you're not trying to go backwards, but allows you to always go forward. So what you need to do is format the drive, and start with the oldest version of windows that you want, and then work your way up. Simply make the partition sizes that you want for the different o/s's and you should be just fine.
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