Originally Posted by liquidsilver
The best resources are probably the two below in my signature.
One unlock allows you to utilize different carriers with your phone. That is SIM unlock. That's what you received from ATT.
CID unlock expands on that allowing you to safely load roms other than those tagged as being from your carrier. That's a weak explanation and the pros here have documented it far better in the Wiki.
Huh? the op didnt say anything about sim
anyway what registry key are you modifying?
there are multiple reasons why a registry doesn't stick.
according to this http://forum.xda-developers.com/showthread.php?t=330322
try powering down instead of using the soft reset button.
if all else fails, make a registry file and put it in the startup folder, since most registry keys take effect immediately.