Due to a few that have had trouble I am posting a link to the exact SD updater I use to convert our inhouse Cingular branded Treo's into ENA versions with the 7.1MB ROM partition. This will update all tokens and firmware. From here you can modify using the ROM Tool to your hearts content.
Link:
http://www.4shared.com/file/17163992...NG_to_ENA.html
This is for "unbranding" not "unlocking". Unbranding allows you to use the generic version of a Treo ROM. For instance you have a Cingular Treo and you want to run the latest 1.20 ENA version.
There are a couple of options to do this.
The first is to modify the Tokens that cause the updaters not to work. These tokens are revn(ex. 1.20) and crnm(ex. ENA). The RomTool allows you to change these tokens. Once changed to match you can then run the desired updater. Example: You have 1.17-CNG, you want 1.20-ENA. If you change the token values from 1.17 to 1.20 and CNG to ENA, you can then run the 1.20 updater. This is the way I recommend.
Another option is to run a custom ROM already put together for the version you want. These do not check versions.
Last option is to run one of Palm's updaters that doesn't check, 1.23 version (I believe).