M11x R3, does not boot continuous loud beeping for 3 minutes or more

If it's just a single beep that goes on and on then it will be the single beep error which is a motherboard error or BIOS corruption. I believe the M11x has the wired CMOS battery instead of the wireless coin battery. Remove this battery, the RAM and the main battery and try holding the power button down for 30 seconds again. Hopefully this will reset the BIOS but it could be a bigger issue if the issue persists.  

If this fails then you can try bridging the two CMOS battery connector pins on the motherboard with a screwdriver. Hold the tip of the screwdriver across both pins for about 10 seconds. I've used this method to reset the BIOS on my M18x. Make sure there is no power though (unplug the charger and battery). Do this at your own risk though. 

You may get a 5 beep error after doing either of these things but that should go away after another reboot. If your single beep returns then you could have a faulty motherboard. Some other guys may have some other advice though. 

CMOS:

https://www.amazon.com/RSRV-Cmos-Battery-Alienware-0F08VK/dp/B01A3XJN6A/ref=sr_1_7?dchild=1&keywords=CMOS+battery+m11x&qid=1595215069&sr=8-7

Service manual:

https://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_alienware_laptops/alienware-m11x-r3_service%20manual_en-us.pdf

Drivers:

https://www.dell.com/support/home/en-us/product-support/product/alienware-m11x-r3/drivers

Thanks so much for the considered reply @mattyb3 . I am not sure what you mean by a single beep. I've made a recording.

It is a long set of discrete beeps, I can discern no pattern. Here is the recording beeping starts 14 seconds in

https://soundcloud.com/barclay-lane/alienware-mx11

Is this the single beep error? I am fairly familiar with opening and soldering laptops. Have done it a few times... so will go ahead and try the CMOS clearing as you suggest, if this is indeed a single beep error

Thanks for the links @Alienware Area-51 ALX 2006 

Thats a strange one. It’s like a beep code on crack. 
Just check that you don’t have keys stuck down. Maybe try booting with the keyboard unplugged. 

I forgot to mention that the keyboard does not work. I am using an external USB keyboard to navigate to BIOS etc.

I think I will try to disconnect the keyboard, it might be causing the problem as you say.

thanks

This guy might have the same problem.

https://www.dell.com/community/Laptops-General-Read-Only/Alienware-m11x-freezes-and-beeps-on-startup/td-p/4243333

Any luck with removing the keyboard? 

Try replacing the internal keyboard:

https://www.amazon.com/Al¡enware-Keyboard-V109002DS1-CN-00MJ7Y-EbidDealz/dp/B0897JX67V/ref=sr_1_2?dchild=1&keywords=m11x+r3+keyboard&qid=1595376721&sr=8-2

Sorry did not update here. This did not work. well tbh, not sure if it worked or not, I tried to disconnect the keyboard but had some trouble releasing it... seem to have gotten wedged fused to the motherboard... now it doesnt beep... but doesnt do anything else either.

I might have destroyed the motherboard... ahhh well, machine did well... put in its time.

Thanks all for your help.

Your welcome.

That sounds a little strange. If you want to head over the the forum at NotebookReview and post some pictures then it may be easier to help you out. The connector shouldn't fuse to the board.

Maybe heat messed it up?

It's possible but it would be surprising considering the type of ribbon cable the keyboard uses. I'm hoping that a new keyboard for about $40 would solve his issue. I've had a similar problem before where a laptop would beep like crazy when keys were stuck down during booting. 

Me too, my laptop would literally play a loud tune while it was trying to boot.