I thought I would post this in case it can be useful to another newb.
I recently used QTParted to add some physical space on my drive to install BT3.
After successfully installing BT3, I realized lilo (boot loader) was not recognizing my original Vista partition. I only had the option to boot into BT3.
The following is what I did to fix it.
At the terminal type: kwrite \etc\lilo.conf
boot = /dev/sda
timeout = 60
#vga = 769,771/773/792
vga = 769
image = /boot/vmlinuz
root = current
label = BackTrack
and add the following line at the end
label = Windows Vista
Save the lilo.conf
In a terminal window type: lilo
It should rebuild with your new config. When you restart you should see the option to boot into both OS's.
Hope this helps!