[marGrietins]

What could be a reason why my experiment with Mpemba effect didn't succeed?
The obsticles were the following: two 100 ml glasses of water (in one - ~45*C warm water, in other ~5*C cold water).
I used a tap water.

[Hertzinger]

That is actually an incredibly flawed statement. Hot water doesn't freeze faster than cold water.
Cold water actually takes less time.

The reason hot water drops its temperature a lot faster than cold water is to re establish an equilibrium in its temperature. Before the hot water can freeze, it has to pass through the stage of being cold water. Perhaps you are confusing this with salt water and normal water, where the salt water has a lower freezing temperature and a lower boiling point. Where as the pure water has a higher freezing temperature and higher boiling point and steaming point.

[Borek]

Perhaps because Mpemba effect doesn't exist?

I don't know if it does or not, I have read contradicting reports. But your experiment is probably about as valid as the original Mpemba one.

[Borek]

That is actually an incredibly flawed statement. Hot water doesn't freeze faster than cold water.

Please read http://en.wikipedia.org/wiki/Mpemba_effect - not that wiki is a 100% reliable source of information, but at least you will know what we are talking about.