I recently went through the dual boot thing without a hitch, but if I had to do it again, I'd do it differently. I'd set up the BT partitions first, and put the window partition last. The reason for this is that Vista has the capability to resize partitions on the fly, and I tried shrinking my windows partition to make a fat32 that both windows and bt could write to. That went fine, but after the change, bt failed to load, as the order in which it mounted the partitions changed, and lilo could no longer find my bt installation. Now, I could have just edited my lilo.conf file, but instead, for now, I just deleted the new partition and reclaimed the space in Vista for my windows install.
The Gparted live cd (sourceforge) is a great partitioning tool.
I have 3 partitions. Sda1 is windows, sda2 is swap, and sda3 is backtrack. All are primary partitions. I installed windows first, then backtrack, and then just edited lilo.conf to let lilo know about my windows install. After you change lilo.conf, you have to run the lilo binary to apply the changes.
Btw, here's the guide I used for dual boot setup: http://www.securitydistro.com/index....=251&Itemid=43