To be clear,
the system will boot "normally" if the drive you are using to test is not connected, meaning you can boot to a LiveCD or Memtest86, should you decide to test the RAM.
when you connect this test hard drive, the system hangs at the BIOS, and won't even allow you to enter the BIOS.
you have only tested this laptop with one hard drive.
These things being true, I would say that either the hard disc controller on the motherboard is faulty, or your test drive is faulty.
Test the unit with a different hard drive... one you know works. I don't mean one you believe strongly should work because it worked the last time you checked, or one that you pulled because it threw errors but you can still access data from when connected via USB converter. I mean a drive you know that works properly the way it should.
If the laptop continues to hang at the BIOS regardless of how many different hard drives you connect, then chances are the controller on the board is bad which would mean it needs a motherboard replacement... and barring getting a new motherboard cheap on eBay, probably means this laptop is relegated to testing and neat experiments with Linux LiveCDs.
If the laptop boots normally with a different hard drive, then you know the hard drive was the issue.
As a side note, eliminate RAM as a possible suspect. Yes, I know... it doesn't seem like Ram is the issue, and honestly, I doubt it is. But, it would not hurt to let it run for a while on a CD of Memtest86