Windows 7: Strange shadows on screen

Suddenly I am seeing a "shadow" effect to the right of text, icons, heading everything on the screenwhether it is showing the desktop, Browser any programs. Did have an Aero theme running but have changed this to standard windows theme. Same problem. Hope you cann see the effect on this screenshot. The shadow is on the message box as I type!

Attachment 93365

I am not sure what I should be looking for here?

Can you see the grey blocks marked in the red circles?

Attachment 93378

No.

I'm not sure I see anything there John. Even a image editing software (Paint.NET) doesn't see it. Its the same white all around.

Maybe you need to get your eyes checked
Just kidding

Can't see it either

Nope, nothing there.

Well I really think I am goibg dippy. On my screen the shadows are very pronounced. On the desktop the shadow against the dark blue is pale whereas against the light blue section in is dark. Against a black background, my pictire viewer for example it is almost white but even putting a snippet file onto a memory stick and putting that in my other XP machine I can't see the shadow. It must be something specific in the monitor though if i take a screenshot one would think that would reproduce on another complaetely independent PC.
Will investigate the monitor later. Haven't tried switching the monitor so will try that first when i return from dog walking. wiil report back later!

I can't see anything either John.

If I'm going dippy then so is my wife as she can see the shadows!
EDIT
Seriously though, it is getting worse by the minute, think I will shut down while I'm out just in case the screen is going duff!