Vista - Cannot write to the registry at all

Any help would be appreciated as I am totally stuck!

Only have one account on Vista Home Premium, which I set up when first loading up the PC - this account is the admin account.

I recently trialled some Adobe software, the software ran out and I attempted to uninstall. An error message came up saying I didn't have sufficient priveledges to write to the key/registry and I couldn't properly uninstall. I followed some instructions and tried to make the key available to access using permissions, this seemed to work. It still wasn't working so I searched the net and came across Revo Uninstaller, and managed to remove all instances of the software.

I then attempted to install some different software and this failed with a similar message - "do not have permission to access the key"...

Today I tried to load up iTunes and now I'm getting the same message when double-clicking the logo on desktop. So I attempted to uninstall iTunes, then re-install. I can't uninstall as I get a key error again, and when I try to install the same error occurs.

Everything points to me not being able to have full permissions to access the registry, but I can't find out exactly how to:

1. Uninstall correctly
2. Reinstall correctly

If anyone can help I would appreciate it - otherwise, I'm going to wait until Windows 7 comes out, wipe my HD and do a fresh install

Thanks,
Tony

Check how it is in safe mode -if the same open regedit go to

HKEY_LOCALE_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall

and check permissions to this key.Administrators group & System account should have full control,Users group -read