I'm trying to install Windows NT 4.0 Workstation SP1 on an unused PC (MSI J1800I, HDD 75GB 5400RPM, Samsung 2x2GB 10600MHz). Here's what I get, along with long beeping:
I have successfully installed it on virtual machine in the past, and I wonder what I'm doing wrong now?
Your particular problem is because NT 4.0 SP1 is apparently not compatible with anything newer than a Pentium 4. However, newer Service Packs should work (and SP6a, the last available one, is known to work).
Unfortunately, it is apparently not possible to slipstream newer packs. The only way to do it is to first install a newer Service Pack in a VM (with CPU features restricted), and then clone the disk to the physical machine.
Paraphrased from this forum thread with a very similar photo: https://www.betaarchive.com/forum/viewtopic.php?f=61&t=33418
That should at least get you past this hurdle. Note that you'll probably also need to find an AHCI driver (assuming a SATA disk) (you may be able to switch the controller into IDE mode in firmware settings), USB drivers, etc..
