WinCDEmu is an open-source CD emulator for Windows that allows mounting CD/DVD images by clicking at the image files in Windows Explorer — both Windows XP and Vista. Once installed, you can mount ISO, CUE, BIN/RAW/IMG file formats as well as SMB network shares and includes a workaround for Windows cache bug. Each mounted image will be represented by a separate virtual CD device, as in MacOS. There is no limit for the number of simultaniously mounted images.
More info: WinCDEmu