laviniuc :
make sure you've plugged it on the dvi or hdmi slot quality is a bit better compared to the standard dsub connector... sounds like you need to calibrate the new monitor and the old one had a better factory default.
it can be also that you are simply used to the old monitor so the new one's resolution / size hurts your eyes...
make sure it's set to it's native resolution on the display settings -> adjust resolution page
I did not get a DVI cable with it, I'M about to go and buy one, I can't find a resolution option in the monitors settings, but under the information tab it says it's set to 1080p, 60 hz. It could be the size, my old one was a 22" this one is a 24", maybe I just have to wait and get used to it