Install the official BlackBerry Desktop Software or standalone BlackBerry USB drivers so your PC recognizes the device in bootloader mode.
The phone does not turn on properly and shows a flashing red LED. blackberry 9780 autoloader
Even with perfect execution, you may encounter problems. Here is the diagnostic guide for the 9780. continuous reboot loops
For the BlackBerry Bold 9780, the autoloader deploys BlackBerry OS 6.0. It bypasses the phone's bricked user interface, making it the premier tool for fixing "Error 507" (no operating system found), continuous reboot loops, or a device that only shows a blinking red LED light. Prerequisites Before Flashing blackberry 9780 autoloader