Is my external HD bootable?

My old laptop died and I took out its Hard Drive which is now readable on my new laptop using a USB caddy. I can access all the files fine - but not run programs from it. I gather I need to boot from the old HD to run programs from the old HD. OK, so I've gone into boot options on start-up but my USB HD does not show, even though USB boot is enabled. I've altered the BIOS so that USB boot is first, I've removed the USB printer connection and I've swapped the caddy to another USB slot. But no change - although this HD booted just fine in its old machine, it is not booting when attached to this new machine. Is there something else required and if so, what?

You cannot remove a hard drive from an OEM laptop...place it in another laptop that is not the exact same model by the same manufacturer...and expect to use such as a boot drive using the Windows version installed on it from the other system.  The Windows license applicable ad the drivers would be totally different.

Louis

Thanks. So, just to confirm, there's no way I can run any programs from the old hard drive? There's no way to get the old hard drive to work, other than access the data files? Is that correct?

Correct.  You can access data folders and files.

Ah well, thanks anyway. Appreciated.