I am talking about in the context of Win NT. SID is an acronym for Security Identifier. Today I needed to change the name of my main box, simple because the name, well, was crap. So thinking back to the last time I needed to change a SID, I used the newsid.exe tool from [what was then] SysInternals and I remember seeing an option for changing the name of the computer. Now I could of simply inputting my current SID, but no, I was in a rush and chose to generate a random key. Big mistake, all my EFS encrypted files (which were not that important anyway, since I don’t use EFS to secure anything important) were made usless, now I could recover them, but to save me the trouble I obtained the old SID from SAM file (C:\WINDOWS\system32\config\SAM), by viewing the security tab, which then showed me my SID. (You will need to truncate after the 7th dash, eg. S-1-5-21-xxxxxxxxxxx-xxxxxxxxx-xxxxxxxxxx|-xxxx <– .The rest is just to do with the user name. The simple way to change the computer name is Control Panel>System>Computer Name>Change.

So there a lesson learn’t, do not change the SID!

Steven