[redhead]

#include <stdlib.h>

Waba.... where in this piece of code does it require the stdlib header ??

#include <conio.h>

Given that this is just a simple implementation I would suggest to use the math header instead, atleast it is system independant, and later on we might end up doing some serius mathmatical equations where it might come in handy.

Matrix2x2(int = 1. int = 1, int = 1, int =1);

That is just plain wrong
You can't create a function like that..

Matrix2x2(float nOne=1.0, float nTwo=1.0, float nThree=1.0, float nFour=1.0);

might be a better aproach, firstof you're private variables are floats, if you're gonna assign int values to them, why the hell declare them as floats in the first place??

void calcDet();

You might want this to return a float, given that the determinant often reveals a value...

Matrix2x2 operator*();

This could be returning Matrix2x2& if I'm not mistaken.

And the calculations for determinant and multiplications are strait out of the box, it's math 101. May I suggest Linear Algebra - Gateway to methmatics by Robert Messer, isbn: 0-06-501728-5 as a good reference.