windows xp os boot menu

i some how ended up with a half install of windows on my hdd and every time i booted it would show me os boot choice menu.

the half install wouldn’t ever do anything due to error missing \system32\hal.dll so i had to choose windows xp from the list which got annoying.

soooooo i went to system properties and disabled os boot menu BUT forgot to change default os now when i boot it automatically tries to start the half install then tells me missing \system32\hal.dll and then reboots

so i nstalled windows to a different hdd and hooked up the old drive and would like to know
1: can i start windows from within the old drive and turn that menu back on
OR
2: can i just change the setting back somehow

i have alot of information on this drive and am not really in place to format and re install(the new drive is only 10 gig and not big enough to hold all my stuff)

thanx