Right, as the author of MG 42 didn't include any type of readme, I took the liberty of converting the finnish one on the official website of MG 42(http://surkimukset.net/mg42).

MG 42 README v1.2

Maschinengewehr 42 (MG-42) is a simple, but addictive singleplayer shoot-out for Windows based systems.
The game is tested to work on Windows 98, ME, 2000 and XP.

The goal is to prevent the allied landing Normandy. To do this, you are given charge of a defence line with machinegun(MG-42) bunkers, highly trained snipers, earth shaking artillery and the fierce Luftwaffe JU-87 divebombers.

New in v1.12
- Code has been optimized. The game should run far better on older systems now. 

New in v1.1
- Options menu, you can disable gore(makes the game faster?)
- The ability to adjust the window setting from the 'Options' menu(you can also change it ingame with the keys 'F8' and 'F9')
- 5 difficulty levels, which affect:
-- Regeneration of artillery and airsupport
-- Closecombat efficiency
-- Landingship numbers and speed
-- Enemy moral
- Game length. You can now choose the amount of enemys(500 - 1000 - 1500 - infinite)

WEAPONS
You can choose a weapon with the numerical keys or by pressing the any of the weapon icons in the weapon bar.

Machineguns (Maschinengewehr 42)
The 'basic weapon', which plays the biggest role(hence the name). When you have chosen the MG, press and hold the left mouse button and move your mouse around to aim. Each MG that is in range, will fire at the given target.
The defence line is made out of 5 bunkers(2 MG's each) and 4 "nests"(1 MG each). If the enemy breaks through the line and passes a nest or a bunker, it will be destroyed temporarely.

Sniper Rifle (Mauser Kar 98K)
With the sniper rifle, you can kill any troop with a single shot. Just aim and click the left mouse button when you have a soldier under the sniper cross.
You can spot enemy officers with the sniper rifle and kill them to degreese the enemy morale, making the enemy either run or stay in their positions.

Artillery
To request artillery, first select the artillery by clicking on the artillery icon in the weapons bar and then left clicking anywhere on the map. A few moments later the deadly shells will shatter anything under them.
You will only have a limited number of artillery, so use them wisely! You will receive more after a certain amount of time.

Divebomber (Junkers JU-87 Stuka)
The airstrike is ordered the same way as a artillery strike, first select the airstrike(plane icon) from the weapons bar, then left click anywhere on the map. The divebombing is efficient against large groups, as it doesn't cover as much area as the artillery does, but kills anything instantly and everything in it's range.

WHEN THE LINE FALLS
The idea is to defeat the allied landing and stop them from getting through into close combat situation. If the enemy gets through, the "knife and grenade" will start flashing in the status bar, this is the sign that your troops are in close combat with the enemy. In close combat, the enemy naturally causes losses to your troops. You can see your remaining troops from the bar with the iron crosses. When the bar hits 0, you loose the game.
NOTE: If a large amount of troops get pass, the damage will be greater than if a smaller number would get pass. So don't let the masses get through!

FAQ
Q: Why aren't the sounds working, or am I deaf?
A: The sounds are under consideration.

Q: Sniper rifle is useless!
A: Use it to sniper the officers in the boats(star above their heads). If you succesfully snipe all of the enemy officers, the enemy morale will go down. The morale is indicated by the enemy flag in the lower corner.

Q: The game is very slow!!!
A: We know, working on a fix.