Disk Defrag

'Ello,

On my Windows XP Home edition it won't let me do a disk
defrag. Every time I try doing it though windows it
says "Windows cannot ops this file: dfrg.msc" and asks me
if I want to search the web for a program that will or
pick one my self.

To start the defrag I am going to Start All Programs
Accessiories System Tools Disk Defragmenter and then
it comes up with that message.

Does any one have any idea how to fix this?

Also on another note can you install a copy of Windows XP
Pro on a XP Home machine just by upgrading it from one to
the other?