Try editing the GRUB.
I triple boot windows 7, ubuntu and BT 5 ..by default BT5 starts on boot ...how can i change it to windows (/dev/sda5)
If you have any difficulties editing grub manually you can install "startupmanager"
I was able to do this a while back with a bit of googling. You can rearrange the order the os's are listed making win the top/default, or keep them in their current order and make win the one highlighted by default.
There's one thing I never understood about grub, I mean, I understand how to edit it and such. It's just that I have MINT and BT5 installed on my netbook. I edited the MINT grub to how I needed it, and it works fine. BUT, if I go into BT5's grub, it's not duplicated from the other grub. What/how is the MINT grub grabbed over the BT5 grub on boot up? Is there a way to switch between the two?
I think the answer in this is adding the menu entries from /boot/grub/grub.cfg to /etc/grub.d/40_custom in the order you would like them to boot then taking away executable permissions from 10_linux 20_memtest86+ and 30_os-prober. Don't forget to issue the command "update-grub" after you've made these changes. when doing this you can also edit the names of the menu entries. If any of this if difficult to understand here's a link for reference---> http://ubuntuforums.org/showthread.php?t=1195275. This solution though a bit more complicated gives you far more control than startupmanager does.