Yes you can follow the steps outlined here:
http://androidforums.com/incredible-all-things-root/427344-2-3-4-root-downgrade-s-off.html
I can not emphasize enough that you need to follow the steps EXACTLY or you will run into problems.
Alternatively htc just added support for their official unlocking tool. It will allow you to easily unlock your boot loader and obtain root access by flashing a recovery image and super user.
HTCdev - Unlock Bootloader
The first method I linked is a complete root and unlock method and allows for easier recovery of a soft bricked phone, however the official HTC method will fit most users needs.
Scotty does a good job explaining the difference here:
http://androidforums.com/3818030-post7.html