had a similar problem.
running windows 7
ultimate 64 bit. and itunes on my computer recognized my iphone as being plugged in. but windows 7 did not. it registered it as a mtp device under device manager. disabling me from from getting pictures off my iphone.
what helped me was i uninstalled the mtp usb portable device in my device manager, which Windows 7 apparently believed was my iphone. then uninstalled all apple softwares installed including apple device manager, uninstalled quicktime
and itunes, restarted my computer as requested by the itunes uninstaller and upon restart without any apple software on there. my windows 7 immediately recognized my iphone as being an apple iphone (finally!).
now i'm going to install itunes again to see if this stays that way.
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November 2009