1. RESCUE THE ORIGINAL DRIVER FILES
One option is to retrieve the
original driver files for the current monitor from the crashed hard disk that "went silly".
You don't explain what faults that original disk had, but even if they were severe it is not impossible that files might be copied off of it, by booting the system into DOS mode using a bootable floppy disk, and copying the files with DOS onto a second floppy disk, using the floppy drive as both Drive A: and Drive B: alternately ;-
COPY C:\FILENAME.BIN B:
There are lots of circumstances in which a hard disk can't start Windows, but can still be read in DOS mode, if the computer is started using a bootable floppy disk.
Where a hard disk is not even accessible in that manner, there are a lot of software programs (data recovery programs) that can scan a damaged hard disk, in order to copy files off of it. For example, look at this page:
http://myweb.tiscali.co.uk/bridip/recovery.htm
There are links on that page to software programs for recovering individual files:
http://myweb.tiscali.co.uk/bridip/recovery.htm#11 2. FIX THE ERROR MESSAGES
You haven't indicated what error messages you were seeing when you tried to start the computer with the hard disk that "went silly".
However, fixes for many common Error Messages are set out in the following link (including fixes for
Blue Screen errors and for
many other types of error):
http://myweb.tiscali.co.uk/bridip/recovery.htm#sectionC
These fixes might either get your old disk working again, or enable you to rescue from it the original driver files for your monitor.
3. UPDATE THE HARDWARE INFORMATION DATABASE
The two above steps probably won't fix the problem, so you can also do as follows.
The fault you've got with the replacement disk (continuous rebooting) might be cured by fixing the hardware database on the replacement disk.
There are notes on how to do that in the following link (scroll down the page a bit to the heading HARDWARE INFORMATION DATABASE):
http://myweb.tiscali.co.uk/bridip/recovery.htm#sectionD
Basically, you may have run into a problem whereby the database on the
replacement disk expects a very particular make of hardware to be present, and its absence causes a reboot. The solution in the above link removes the references to any non-existing hardware.
It's important to have the correct driver files for the current monitor ready at hand (i.e. those for the monitor actually present). But do NOT copy them onto the replacement hard disk until AFTER going through the removal procedure in the above link, which removes the out-dated references in the disk's old hardware database.
Once that's done, then copy the monitor's driver files to C: root. Then a re-start of the computer should cause Windows to notice those new hardware drivers.
The procedure is analagous to uninstalling a software program before installing a replacement version. Its effect is to update the hardware database with the new information.