The easier way is to clone the Win 7 to the SSD. That is if the to total amount of data on your Win 7 INSTALLATION is less than the capacity of the SSD.
But yeah, If you have the original installer CD, just switch the drives and boot from the CD and proceed with the installation. You can buy an SSD to HDD adapter to fit the SSD in the hard drive bay, but that is not really important. You can tape it or tie it securely inside the case..
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