won't boot

Thinkpad X2, 16gb Ram, 500GB drive Recently I switched above HD with a 1tb ssd and installed windows 11 pro. I still want to boot up Win7. So I switched the HD again and this time Win7 did not boot up after posting. It stops on the black screen with a cursor blinking, top left. What's the fix here?

I must have been struck by a nasty virus. When I boot my computer, I get a screen with the following message instead: "Info: the boot selection failed because a required device is inaccessible." I can't boot in Safe Mode. Windows is not found. I booted my Win7 install DVD and went into...