Also check the BIOS is set to allow automatic allocation of resources. Some have a "manual" setting for legacy cards which may be causing the problem as it won't allow your new card to use the resources it needs. (Watch your initial screen for which key to press during boot-up to get into it. If you're not sure though, don't mess about with it as you can cause a major foul-up). Sorry if you already know how to suck eggs! Good luck.
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May the Force be with you - and may Gravity treat you gently..