This unlocking solution covers for Htc Tattoo, Htc Hero and other branded Orange with Android OS.
Download the 'ROM' Update for your HTC phone.
The 'ROM' can be downloaded from official website of HTC.com/uk/
Or from below link.
ROM for HTC Tattoo
ROM for HTC Hero
Install HTC Sync
Now Run Rom upgrade utility, and wait till setup finished.
then put non accepted sim card. Enter the code.