Now and then this happens on my Windows Seven PC. I wrote a lot of programs that open Explorer windows. To make cutting Explorer copies back to one I wrote a small utility that closes all but the oldest(so you don't get your tray apps closing etc.) if you click OK. The zip has both 32 and 64 bit versions of ExplorerReset. You may download from this page
The zip includes AHK_L source code. You don't need it. The 32 and 64 bit copies are already compiled. But I put the source scripts and custom icon in the zip so you know what's in the programs. You may customize it if you wish.
edit: I just updated the zip to include a Readme.txt file. It's self-evident how to use the program. The usual "free for you to use at your own risk" disclaimer applies.