hi im a newb with this stuff i bought an acer iconia a500 used and its a demo. i researched a bit and tried to use one of the full rom downloads to sd card to reinstall a new system or whatever but i have no clue what im doing and would appreciate if anyone can give me a step by step. maybe i did something wrong but everytime i download the full rom onto sd and hold the volume down and power button it acts like its going to work and then pops up with android and triangle with exclamation point. please help im confused and aggravated.