Using the same computer, same OS, there's no problem Disconnecting the SSD, then connecting the older HHD to boot up to Windows 7. Then get the files or drivers you need on a USB flashdrive. Then disconnect the older HHD, and reconnect the SSD. Only one connected at a time.
Assumming you have a retail copy of Win-7 and it required the online registration of the new installation after completion.
Yes, you are right. Thanks for the reassurance. I did exactly this, no problems. Thank you.