Im booting backtrack 4final from a usb since my computer im using does not have a cd drive but anyways when i go to install bt4 to my computer i want it to dual boot win7 and bt4. When i get to step 4 i think it is where i get to decide how much space i want to choice to dedicate to bt4. When i move on to forward to the next step i get a error when it tries to partition.