You can find an online copy of the manual. For example, I found one using Google at
http://www.prolink-usa.com/english/manual.html
If you know the model of your motherboard, posting that might help, but it sounds like you have a PCI card and no free PCI slot. If you have an AGP slot, a different model of card might help, but if you don't have either the only way to go is with a new motherboard. That might not help either if your processor can't be removed from your old motherboard, as some celerons can't be. So, if you buy a new motherboard you may have to buy a new processor with it. If you end up doing that, make sure that it's compatible with yoru current RAM chips, or you'll end up buying new ones of those as well.
But for now, try posting your motherboard model if you know it.