Brutal Doom v19-How to see the health and ammo on the HUD

With DOSBox you should have no problem

Here's a wiki

There you'll have some source port to play your favorite game :D

Note:

Doom requires a fairly fast computer to run inside DOSBox, but many ports of its source code exist for modern Operating Systems, so you may find more luck downloading one of them instead. Because Doom makes use of your sound card and potentially Modem, you should take care to match your dosbox.conf setting to the settings found in the SETUP.EXE found inside your Doom folder. For the most part the default options will work, but if you are making use of the Gravis Ultra Sound or MIDI audio devices you should pay special attention that the DMA, IRQ and Addresses all match.

To find the Doom level, you will need to travel to Gearhead Vault, within Subway Town. Once you're able to access this level;

• Kill all enemies and head towards the area near the end with the computers
• Activate seven of these computers (use video for reference as to which) - you will hear a sound from DOOM for every computer you interact with
• Once activated all computers are activated you will hear a second sound effect from DOOM
• Head back to the start of the level
• A previously locked door will now be unlocked
• "Use" the teleporter to transport to E1M1

Here is a youtube video detailing how to find this hidden room:

Finding this secret level will also allow you to find the Doom Marine bobblehead item: