Access Denied...how to get control of MY vista/win7 computer?

I need a pointer to a tutorial on how to get back
control of my computer. Have same problems in both
vista and windows-7 beta.

Access denied for most of what I want to do.
I'm trying to make hardware and software work in
windows-7. Permission problems, failure of older
install programs to execute, unable to register dlls,
it's a nightmare. Compatibility mode helps when you
have access to the executable file. When it's buried
inside an installer..not so much. Problem is same in Vista.

Here's a current situation.
wmplayer.exe is getting started by whoknowswhat
and interferes with other programs that need access
to the cdrom. I NEVER want to use wmplayer...although
I don't know what the side effects of turning it off might be...

Ok, let's try renaming wmplayer.exe so it can't run.
Sounds simple enough...but noooooo!!!
As administrator, I can't edit the file name.
I can't give myself permission to access the file.
I can take ownership of the file, but i still can't
rename it. I still can't give myself write privileges.
Seems like I'm always running into Access Denied problems.

There's a trusted installer group, but can't seem to
get added to it.

What can I do to make Vista give me back control
of my system so I can use it the way I want it?

Just to head off the trip in the wrong direction...
I don't need a lecture on security. Security that prevents
use of the machine is not helpful. I need help
REDUCING security so I can use my own darn computer.

Thanks, mike