make sure you got an uptodate itunes first then try this:
Disconnect iPhone and close iTunes.

Go to Start, Control Panel, Administrative Tools.

Under Administrative Tools, Go to Services and look for 2 services.

Apple Mobile Device
iPod service

Both services should be started If they are not, start both of them.

Start iTunes and wait for it to finish loading.

Reconnect iPhone. Voila! It should see your iPhone.


Or

Leave the phone connected to the pc then restart itunes after.