IRQ means Interupt Request. Basically every piece of hardware in your computer has one assigned to it. Think of it as a way of your computer identifying a certain piece. If more then one piece is using the same IRQ then sometimes this can cause problems if the hardware doesn't share. Certain slots share IRQs with certain other slots so it is important which slot you seat cards in. Basically, its a good idea to leave PCI Slot1 empty (the one right next to the AGP card) since this would share with the video card and in my experience that is usually a bad thing.
Anyway, I personally like sitting the sound card in slot 3. But it really depends on your mainboard too...
If you would like to describe your problem in a little more detail and tell what kind of system it is you are on that would be helpful. For instance, what motherboard and processor are you running? Sound Card? Video Card? All this info is helpful. Also, what kind of crashes? Is it simply going into a hard lock where you have to reset the power or is it crashing out to windows or resetting on its own?
Also, if you goto My Computer/Control Panel/System... and then click on the Device Manager tab it will bring up a list of hardware that is connected. From here you can update drivers manually, check the resources being used by different cards, and a few more things. If you go in there and see a conflict then you know what the problem is... unfortunatly sometimes things can be using the same IRQ and not actually conflicting (atleast as not as far as windows can tell) but it still causes problems.
Anyway, I hope this info is useful and please post back about your system speck and problem so we can better diagnose. Thanks