please make sure that you have installed driver properly. adb won't work if you install Google driver as single device driver, and if you install HTC driver as single device driver, DiskDrive will freeze your phone (but adb works directly).
our phone is "USB Composite Device", and windows has this driver included. you can try install it. after that, your PC will find new devices: one for adb (both Google and HTC's drivers will work), another for USB mass storage, and others don't have drivers (I will remove them if these two devices cause troubles) .