What is this "root" thing on an HTC EVO 4G. Just got phone last week. System 2.2 Laptop kept getting a pop up screen Re. need to find additional drivers for ADB (?) Called customer service, told me to get "uncorrupted" 2.1 system flash at Sprint store. Went to Sprint store. The flashed 2.2, said not able to flash 2.1. Phone now seems to be working, but I don't really know, since I have no history with this phone various system upgrades. It's new to me, as of last week. So, what is this root thing ? Where can I get/read a primitive, newby, type instructional on this. Thanks.