The program recommended by Ethel is useful but you can control all of your startup programs as follows:
Click 'Start'
Select 'Run'
Type 'msconfig' (without the quote marks).
Click 'OK'
Select the 'StartUp' tab
Look through the list to identify the most likely cause of the System 32 window appearing.
Click to remove the tick alongside the item.
Click 'Apply'
Click 'OK'
Restart your computer to see if it's worked. (If not, follow the same route and try something else).
Chris