want to install two operating systems on one hard drive

_kaos_

Honorable
Nov 20, 2012
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You need two partitions

If it's only Windows, install the older version first.(XP<Vista<7<8)
In case of 32-bit/64-bit, install 32-bit first if they are the same versions(eg. win 7 32-bit and windows 7 64-bit)

If it's Windows & Linux, install Windows first.