Does Windows kill the "bootability" other secondary hard drives it finds with the same OS on?

Hi,

Does Windows kill the "bootability" other secondary hard drives it
finds with the same OS on?

Just I had a old machine with Windows 95 OSR2 on, I then upgraded the
HD, installed the same copy of Windows on, and used the only bootable
hard drive as a secondary, to transfer stuff over, and as a backup for
important stuff. Then got a new machine. But now I've come to reuse my
old machine for the odd bit of internet access, I've put the original
HD back in, but I get the message "drive is not bootable" (or words to
that effect). I dont recall deleting any part of Windows on the old
HD, but it was all a while ago, so did Windows on the newer HD kill
it?

If so, do all versions of Windows do this? and do they just kill the
same version of Windows with the same serial number? or do they kill
the same version of Windows with any serial number? Or even kill any
version of windows with any serial number on a secondary HD?

Hope that all made sense

Thanks