To install Froyo manually on your Droid Incredible all you have to do is follow these steps:
>Check if you are on a stock ROM as this update will work only if you are.
>Download the Official Android 2.2 Firmware.
>Make a copy of the downloaded file to the root directory which is your microSD and name it as “update”.zip.
>Switch Off your phone. Now reboot it with Volume down button pressed.
>Now in the bootloader screen select recovery using volume keys to navigate and power button to select.
>Upon seeing the “/!\” symbol press volume up and power to show recovery options. As earlier use volume keys to navigate and power button to select “apply sdcard:update.zip”.
>When the installation completes you will see “Install for sdcard complete”, now just select “reboot system now” to finish.