I do have a large amount of "unmovable" files. Still doesn't explain why 3rd party Degrag programs work, and native Windows won't."
Perhaps it does if Windows is blocking access to these files by the Windows Defrag program?
Have you tried the Built-in Administrator?
This example might or might not work for you with your program it uses the built-in Administrator account to perform the install?
"It seems that the "Run as administrator" command only gives you some administrative privileges, and they're not enough to install Java (and OpenOffice, by association). In order to get around this, you need to actually log into the built-in administrator. Open a command prompt with admin rights by clicking start, typing cmd into the search/run box, and hitting CTRL-SHIFT-ENTER. At the prompt, type:
net user administrator /active:yes
Then log out of your regular account and back in as the built-in administrator, where you might be able to install the program. When you're done, log back into your regular account and, for security purposes, disable the built-in administrator account using:
net user administrator /active:no