Usually that is caused by changing your resolution at some point -- when the CS is closed the current window positions are kept and the next time you launch they are drawn to the same location -- if your screen size has changed then that location may acyually be off the visible screen so you can not find it -- deleting the .ini resets the position to default (you can actually go into the .ini and change the setting also - which is better if you have other non default settings in the ini !)
#khettienna - if you want to get rid of the render window go into the ini and set the location to somewhere that would be off the screen and you can do this intentionally so it is not in your way !
The settings you ned to look for are :
Render Window X=76
Render Window Y=462
Render Window W=1454
Render Window H=1003
Changing X or Y to a number larger than your screen size will draw the window out of sight !