how to delete a stuborn reg key please

Try Registrar Lite (free)
Registrar Lite - Free software downloads and software reviews - CNET Download.com
It works with Win 7 too.

For future notice, you can also boot into another OS (Or WinPE disc if you have one!) and load the hive file you want to edit and then reboot after unloading. it's an old trick "modifying" registry files outside of windows. You can always google this answer, as it's a common question.

Off Campus : Edit the registry on a mounted WIM
Edit the Vista/Win7 install Registry (good for custom discs with pre-installed programs).

Mount registry hive? - UBCD4Win Forums
RegPE will mount the currently installed windows and allow for edit. =)

Really all you need is another OS and mount the hiv files, edit them, and unload them then boot into the system you are editing.

IE lets say I have 2 OS's running on the same computer. Win XP and Win7/Vista, k? I want to edit Win7 registry files, but I can't do that because it's protected. How do I circumvent this? Easy, load the Win7 system.hiv file in windows XP! You do this by:

Start/run regedit (or regedit.exe)

Now go to the hkey_local_machine. Select it and go to file/load hive. They are located in "Windows/System32/Config". So I'd load X:\Windows\System32\Config\SOFTWARE.HIV.

Though I give additional warning when editing HIV files that aren't in use.... If you screw this up it will not boot. WILL NOT. Though if you are comfortable editing the registry and know how it works this shouldn't be too hard for somebody with know how. This is the only way to really edit the SAM file, which is why I know this and the only reason... Otherwise I'd just do it some other way. But this is a method that you can use that will always let you modify your registry without windows complaining.