You had dual boot: mint and BT...So far so good..
Now you want to use BT as your main OS?..Is that correct?
Did you delete the 2 paritions or still have dual boot?
You could have done the next in case you still have dual-boot:
1. Recover the BT5 grub (use any debian based or Ubuntu live dvd) and it will be your main OS.
2. Delete the Mint paritition.
3. Run os-prober and update-grub when in BT5.
If you deleted both partitions, I suggest you use a live DVD to install BT5, but record the dvd at the slowest speed possible.
If you want to use a USB live, read wiki to make a usb live. I use the Universal USB Installer (pendrivelinux.com) and it is quite easy.