If you get a screen with 'Download mode' then you've entered the wrong key combination. Download mode is for loading a Rom, e.g. rooting.
For a T-Mobile version you use volume up + volume down + power
Background music by:
Artist: Tunguska Electronic Music Society
Track: Project-Scorpion - In Depths Of Ocean
Tracklink: http://www.jamendo.com/en/track/761824