Leave your Thrive disconnected from USB until instructed to plug it in.
Enable USB Debug Mode
In Settings, go to Applications > Development > USB Debugging. Make sure that is checked.
Download and Run the DOS Batch Script to Root
Download the latest DOS Batch Script
Connect your Thrive by USB, and when prompted to install drivers, choose the ADB drivers located inside the ZIP package. If you are not prompted for drivers, ensure that you enabled USB Debugging mode.
Now, run the Thrive Easy Flash Tool batch file (thrive_easy_flash_tool.bat). Choose option 1 to Root your device. And follow the onscreen instructions.
It really is as simple as that to root your Thrive, so don't be scared to dive in, and enjoy the benefits of a rooted Thrive.
I realize these instructions may seem simple to the vets here, but for those of us new, there is so much information our there (not a bad thing at all ) that it can be a challenge to find the right procedure.