What model is the HP PC?..

Any chance of using System restore to prior to the monitor failure?
(this is to eliminate some areas of the machine - the issue could still be the Driver for the video adapter)
If that shows no changes - ie: all symptoms remain - you can restore back to current..

One of the tricks to HP/Compaq video adapters was to uninstall the original drivers, then install the new drivers (esp when there is a persistent issue like this)..

The reason we asked for the model of the PC - is more to help us identify if there is a Manufacturers driver that may help you work around the issue..