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Thanks man, it turns out avast thing is a coincidence, the problem stems from a lack of communication between a new update from Microsoft and Nivdia latest drivers, the nvidia driver was listed and optional and hence not installed with an update to vista core system that then cause the problem because system video drivers were one month older than required. Problem solved by uninstalling all nvidia drivers, monitor drivers and installing new one then new monitor then all was good.

cheers for the help