You were installing unstable old OS and Beta OS which break frequently, as a matter of fact, muti boots is the only way to use those old OS. I have old machines I "dedicated" to Windows 9x/Me but they are not the only OS on those machines, I boot into Windows 2000 to image/reimage Win9x/Me partitions on those machines all the time, because old OS's break "all the time".
When you install any OS onto a relatively small partition and make an image of that small partition onto another hard drive, all you have to do is reboot into another OS and reimage in less time it takes you to go on a short bathroom break. Couple of minutes. That's a lot shorter and easier than reinstalling / installing from scratch. That is also quicker than diagnosing the smallest of problems.
If I have a problem with Windows Vista/7/8, even a slight hickup, I reboot into WinXP and nuke them and reimage them. I can't imagine using a computer without doing that. All problems are solved in two minutes like that. All problems that ever come up.
From Windows XP, you can image Windows 8, bonus being that Windows XP is not dependent on BCD like Vista and Win7/8 are so if something goes wrong with that, it's easier to just reboot into WinXP and image modern OS's from WinXP without even looking for and using startup media to fix the problem.