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first change the jumper to the slave drive and install it as a slave drive. boot up your machine and use program like partition magic to copy
your window's directory to the wd1200jb drive. after it's done, swape the 2 drive and change the jumper settings. the machine will boot up
using the wd1200jb. then you are done >>
That may notwork if that's all you do. You must make sure the new partition is active, primary, and has a valid MBR if you want to boot from it.
Partition Magic sometimes does it, sometimes not. With Win XP or 2k you can check in the disk-management snap-in.