n00b. Tri-band GSM, not Quadband. Good luck getting it to work on US Networks.
http://www.htc.com/www/product.aspx?id=46286
Network HSDPA/WCDMA:
Europe/Asia: 900/2100 MHz
Up to 384 kbps up-link and 7.2 Mbps down-link speeds
Tri-band GSM/GPRS/EDGE:
Europe/Asia: 900/1800/1900 MHz