lost all data trying to install new rom

[drew454U]

ok i am 100% new to this, i tryed to download the new rom but before i did i backed up all my data and even pulled my SD card to be sure. i then downloaded the new rom to my phone. then hard resetted. when it came back up i checked and it still had the old rom. so i hookled it back up too active sync and it saved my new data, which was nothing since i just hard resetted, over all my old data. 100+ contacts lost. what did i do wrong??? i appreciate any help thanks