Answer:
the best way is to partition your hard drive, or you could run a dual boot on the same drive. basically start in dos,type- fdisk /?. read all the help. you can also use a 3rd party prog such as partition magic / boot magic. their are many ways to do this some are MUCH BETTER THAN OTHERS, and none of the answers are short-especially if you are trying to keep the data you have. if you are going XP/98 you need to do 98 1st, the XP will take you through it for the 2nd OS. if your going xp/7, after xp is installed insert the 7 disk, and it will take you through it. I would have several partitions, 1ea-data,os1,os2,recovery etc