I have an HT omega striker, used it conjunction with a [analong] senheisser pc165 I think it was, worked well.
There is this Logitech Z cinema 2.1 system, I was wondering does it use it's own built in sound card, onboard drivers are not enabled for my motherboard, so will it work with my ht omega striker or no?
Is it possible to force it to use the sound card in windows 7?
Yes, your Logitech USB speakers have their own audio decoder and completely avoid the soundcard(s).
It looks like there only Vista Drivers for it, hopefully they work in 7.
In Vista all you need to do to switch between outputs is to go into the Sound control panel and select it as the default device, should be pretty similar in 7.
I do this in Vista for switching between an old X-Fi (surround speakers) and a Xonar Essence STX (K701's), works like a charm.
A shortcut on your desktop will speed up the process...