There wont be a clean break as the operating systems would share some files/
directories when installed to the same partition. Best to blow it all away
and start a new install.
By default Windows XP installs in the \windows directory. First Control
Panel|System|Advanced|Startup and Recovery, choose the correct System
Startup option as default, then you'll need to delete the options you want
removed from the boot.ini, it's a system, hidden file in the root of the
system partition. So you'll need to show-all-files, hidden, system in
Explorer. You should end up with something like this (below). The timeout
value is not functional when there is only one startup choice. Then you can
remove the %windir% directory that your currently not using from drive. By
default Windows 2000 installs into the \winnt directory which you can
delete.
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\windows
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\windows="Microsoft Windows XP"
/fastdetect
