No i have not use any programs that change the shortcut overlay icon

Basicly, if i download a change the icon to be transparent, it will be, till the next time i log on... if i download a transparent .ICO file, it is transparent, but if i download transparent .PNG file, it's black :S Allthough, when i was on XP i used WindowBlinds to make my system look like Windows 7, there was one thing called "refresh icons cache" or something like that... Is there any posibility that that SOMEHOW stayed here when i switched to Windows 7 and SOMEHOW does this? Btw. i don't even know what that program did, it was just there with other things in the theme i used with windowblinds...