android_winusb.inf fine was missing in my installation of XP. copied one from net. But in the meanwhile I also installed Android SDK. Then reset the phone to it's original settings and chose ADB as default USB connect mode. It installed drivers again and PC suite, edia sync etc started working fine with XP. Connected the same phone to WIn 7 pc at home and it worked with no problems.
In my opinion:
1) Reset the phone and connect.
2) If that doesn't work copy android_winusb.inf file from net in to Dell Aero/drivers folder.
3) There are 2 exe files. Run the one with gui
4) If nothing works, install Android SDK and select download of files for Android 2.1, 2.2, 2.3 after installation. Reboot and check