Perhaps during the switch of HD's from one computer to another the boot process may have been altered????? Make sure by going in to the BIOS of the computer that now won't boot up properly that the hard drive is in the first position of the boot process.
"Sort of" is harmless "Sort of". Is a filler. But sometimes, "sort of" means everything. Like after "I love you" or "You're going to live" or "It's a boy".