Windows Vista Screen Grabs

Guys,
Need some help here. Every now and then I get an on screen message saying:
Unhandled exception has occured in your application. If you click Continue, the application will ignore this error and attempt to continue. if you click Quit, the application will close immediately.

Could not find file 'C:\Windows\screenshot20035jpg'.

Details:

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

When I look in the Windows folder on my "c" drive I discover there has been taken a screen grab and it is saved as a JPEG Image.

Can anyone tell me what is happening here and can I stop this. I am concerned that someone is trying to hack my laptop.
Guys, let me know if you need any other details.