No screen or keyboard/mouse use after new CPU and motherboard installation.

What i7 chip did you get? Probably should not have got a H81m Chipset if you got a Gen 5 i7 CPU or Devils Canyon Haswell Refresh - you'll need to update the BIOS to make it work, but first you need it to work to update the BIOS....

No bud, you will get absolutely nothing until you put in a compatible processor. Once you buy a Haswell chip (that is not a haswell refresh chip) and install it your computer will boot right up. You can use that chip to download and run the bios flash and then you can put your i7 in.

NO because the 1840 is a haswell refresh chip as well get the 1820

Yes you had it all right except you picked another haswell refresh chip, but that's alright. And not annoying at all, we all enjoy helping out.

Be sure to do that, GL!

Ha ha, yeah, unlucky...it's quite scary how much the guys at PC retail and component stores really don't know about the stuff they sell you. Research, research, research - Google is much smarter than your average PC repair guy

Technically he wasn't wrong, the chip will work but not without a BIOS update unfortunately - but yeah, grab a board manufactured in the last 3 months of 2014 with a 97 or 99 chipset and you should be apples. AS soon as you get it up and running, update the BIOS.

I have an i7-4790k on an ASUS Ranger VII Maximus board - still needed to update the BIOS to get it stable after everything was up and running.

I am just going to go ahead and give you a brief explanation of how the chipsets work and differ.

It will not work out of the box. It will work with the bios flash as long as the i7 is a socket 1150. As I said above, once the bios is flashed it will work just as well as any other board. And you would need a non Haswell Refresh (normal Haswell) chip in order to achieve that. An H81, H87, Z87, H97, or Z97 board would all support the chip, and none of them inherently allow the chip to perform any better than the other.

You notice there are two letters? H and Z? Z chipsets often sport more features than their H counterparts, the key feature being that multipliers and XMP profiles are unlocked to allow you to mess around with the clock speed of your memory and CPU (overclocking/underclocking). Z chipset boards are paired with K processors. For instance you probably have the i7-4690, if you had the 4690k you could overclock that chip on a Z chipset board.

If you have any socket 1150 i7 then it will work with a bios flash. I agree you could return it and get an H or Z97 chipset board and that may turn out to be the better option, but you should compare several Asus boards side by side on Asus's website and decide exactly which extra features you want to pay for. Here is Asus's support list for the H81M-E, all the Haswell and Haswell Refresh i7 chips are on it.

http://www.asus.com/us/Motherboards/H81ME/HelpDesk_CPU/

If you go to Asus's site and compare a few of their boards side by side you can decide exactly which board will work for you. Perhaps an H97 or Z97 board is what you would like. For instance, one could get the Maximus Hero Board, or they could opt for the Asus Z97-A. The board is $150 less expensive but still boasts 4 fan headers, the same quality capacitors, and everything you need to overclock, that other $150 goes into superfluous features you may or may not ever use. If you don't have a K variant of a chip there is no need to get a Z chipset board, and that would be a waste of money. The motherboard and PSU are the backbone of any build, do your research and get exactly what you need and you are setting yourself up for success.