Strange Error! system.nullreferenceexception

Hello

I am wondering if anyone can shed some light on the following error message:

"An unhandled exception of type 'System.NullReferenceException' occurred in Unknown Module.

Additional information: Object reference not set to an instance of an object."

Now, this happens everytime I try and run any application. I have opened Visual Studio requested to create a new Windows Application - I run the program and this occurs (I haven't even added a control or looked at the code). When i do add a control it still occurs - it happens with everything - i have downloaded sample projects from Microsoft and it happens, I have reinstalled vs.net, .net framework and Windows XP and still no luck - anyone have any ideas?

The thing which is common in every windows application is a reference to :
system
system.windows.forms
system.data
system.xml
system.drawing

these references for a console application are

system
system.data
system.xml

so, try buildin a console application and you may find out where is the reference problem. by the way, are you sure you have no corrupt installation?

All sorted out now!

After reinstalling visual studio, Microsoft advised me that the uninstall does not remove everything - they told me to delete numerous registry keys, folders e.t.c and start from scratch - it now works! Only took them 3 months to let me know this but there we go. Thanks for your help anyway