Ok, with the release of the Sprint and Alltel V3M's, this forum has gotten pretty hectic. I have decided to create a thread for the most important part of any process: getting your phone installed with the correct USB drivers.
Verizon, Alltel, USCC - V3C/V3M
Connect your phone to a usb port on the
back of your computer to avoid conflicts. Run DriverTool4.21a (attached). It will say V3C, and that is fine. Let it choose the driver automatically when prompted. It should install usbsermpt.sys. If it does, it will look like this in Device Manager
If you are not having success with that method, try doing the same method with your phone powered OFF.
Sprint V3M
To the best of my knowledge, the Sprint V3M needs the drivers included in Motorola Software Updater (MSU). The program is free. Connect your phone to the computer, run MSU. It will install 4 drivers. Let it choose the driver automatically for each of them. Once done, MSU should show your ESN, and say N/A for the two entries below. In Device Manager, it should look like the following. Note: You might need to run DriverTool4.21a as well if the process didn't work.
Syncing your V3M with WMP10 (From Mark's Site)
Download mtpfix.zip (attached)
Disconnect the phone from your PC, and leave it disconnected.
Turn your phone OFF.
Shutdown/reboot your PC.
When Windows starts up again, get logged in BUT DO NOT Open/Run/Launch any applications.
RUN the MTPFIX.exe you just downloaded.
Turn your phone on.
Reconnect your phone to a USB port built into your PC.
On the phone, go Get It Now -> Get Tunes and Tones -> Sync Music. Windows may try to install additional drivers... If it does, wait for it to complete, then start Windows Media Player on the PC.
If you have any questions regarding any of what was described above, please post them here.