In what specialists are calling a "dick move", it looks like Microsoft removed that functionality in Vista and Windows 7. Here's what Google gave me - registry editing in Windows 7! http://www.winhelponline.com/blog/change-file-type-icon-windows-7-and-vista/
Visceral: I dont have any major issues with 7. i just dont think either OSX or 7 are all that great. both still have things which could improve. 7 has however added the things i missed from OSX.