Such a problem is very common in Windows systems.... Try to figure out what you recently installed on ur machine .. sometimes u install an application which doesnt fit well with other components in Windows Environment... Whenever u try to start windows explorer it gives an error message...isnt it.. .. A particular code of the newly installed application might be giving the problem...Also this is not the process running exactly otherwise the tools that u have used till now would have reported it... Try to repair ur windows explorer from ur boot CD ...
May be the things will work..