OK - I've wasted several hours today trying to sort this out - It's now time to throw it out there...
We've got a HP dc7800p SFF. It fell over and died and has had a Windows reinstall. The dual monitor setup now will not work. The machine recognises that two monitors are connected, but one monitor does not receive a video signal.
Setup:
It's a run of the mill PC running Windows 7 Pro (32bit). The video card in question is a Nvidia GEForce and I've tried it with the default windows drivers - plus I have been to the Nvidia site and downloaded the most recent driver too. Plugged into the video card is a HP DVI Y Cable DMS-59 to Dual VGA Connector.
Device Manager shows a fully functioning Video card and monitors - but also listed in there is a PCI Serial Port & PCI Simple Comms Controller without drivers...
Making me crazy!