If you're really stuck...and I mean really really really stuck -there is another way of doing it.
However, I must stress that if you;re doing this on a computer that doesn't belong to you -please think twice before acting upon this, ok?
However, I also stress that I have ot tested this on Win NT boxes -e.g. Win 2k, XP, 2003 ETC, but i suspect it won't work on those machines anyway.
What you need to do is find the files USER.DAT and SYSTEM.DAT.
They are naturally hidden 'system' files and you will need to go to explorer and select tools, folder options and uncheck 'hide system files' and make sure 'show hidden files' is allowed.
Then refresh the search and look for USER.DAT and SYSTEM.DAT. These files are what make up the registry for a WIN computer.
Now, delete them.
Trust me...you really do have to delete them.
Restart the box and log in...you'll get some message saying the registry has been tampered with. Ignore this. Instead, press ctrl + del and get rid of the box. You should find that now you have no restrictions at all -e.g. you can access regedit, etc...
When you restart, everything will be fine.
However, I'm aware that certain registry programs may ell pick up this weakness and re-copy the .DAT files...you may have to disable these programs first before restarting the machine.
If you can, access 'msconfig' from run menu and click on 'startup' -make sure you uncheck all the registry scanners you can find there.
Now you shoudl be fine. ;-)