Same way...netuser
I believe that is how I DISABLE all of my Home users in Vista/Win7. In XP, I try Ctrl-Alt-Del twice to try to get the log box to appear; if that doesn't work, I reboot into safe mode and wallah!
I always give the hidden Administrator an impossible to crack password, and then disable it using the command line in Home editions. Their will be no account controls in the admin tools on those versions, of course. I either record this password in my records, or put a post-it inside the system unit, so they can't lose it.
This has kept many of my clients from getting cracked by malware on XP installations. I figure it can't hurt on Vista/Win7 either. So far I've never had to re-enable it and log in to do anything for the client.
