Using the one IRQ

Is it normal for many devices to be sharing the same IRQ. The following share IRQ 11:

Video Card
Sound Card
Modem
NIC
USB Controller PCI Parellel port
Running Win 2K.
This is a new computer and is not playing games correctly. It keeps crashing and sometimes it even shuts down. One particular game when staring the CD, it flashes on the screen for a moment and then is gone.
Can anyone help me with this problem please?

Thanks

Mil