I never worked with BCDW and didn't try it, but you can try the following:
Just boot ISOLINUX (see that /boot/isolinux/isolinux.cfg exists):
\boot\isolinux\isolinux.bin ; Ultimate Boot CD 5 RC1
Or try this command line, instead of the one you have:
\boot\isolinux\isolinux.bin ; Ultimate Boot CD 5 RC1 ;; /boot/syslinux/menu.c32 /ubcd/menus/isolinux/main.cfg
I am not sure if BCDW will work with this last line. UBCD50RC1 uses a much recent version of ISOLINUX than the one available when BCDW was coded.
But I don't understand why it would boot grub4dos
BTW, why are you still using BCDW?
Download Ultimate Boot CD v5.0
Use Parted Magic
for handling all partitioning task: http://partedmagic.com/