i don't understand why when people are having issues/problems with booting they think
I know.... a bios update will fix everything! only to realise after the fact they now have a bigger or multiple issues
as aFYI, early bios releases did not support some v3 cpu's this was added in 2.40.2.41 bios updates
if you had simply reinstalled the original cpu and done a bios update all would have been fine. you appear to have learned this lesson so i will not dwell further on it
since you tried to do a bios update while having a major problem you may now have other and more severe issues try the steps below and hope for the best
i recommend you reinstall the original cpu
then do a full factory reset by removing the power cord, pressing the pwr button for 15sec then removing the "cmos" battery and then pressing the small cmos reset button on the motherboard for 3-5 sec
now, reinstall the cmos battery, pwr cord and power on if you get to the bios screen STOP do not try to flash instead note the current installed bios revision some systems require you to perform a intermediate bios update before the latest bios can be installed (checking the hp docs on your bios does not show this is required)
once you know the current revision, you can then update to the current bios using the existing bios's update feature
this requires you to have the new bios on a fat32 usb key and the needed bios image can be found in the extracted bios SP file in the dos folder copy the xxx.bin (or .rom) file to the root of the usb stick
if you can not boot into the bios, note any system beeps/flashing light sequence and post them here
DO NOT ATTEMPT TO FLASH A BIOS UNTIL YOU EITHER HAVE A BOOTABLE SYSTEM OR YOU HAVE DETERMINED WHAT THE CURRENT ERROR IS......
SDH has posted a crisis bios recovery procedure, search this forum for it also note the current HP recovery docs you have might be wrong in how/where to place the recovery bios file, again SDH has noted the correct procedure to follow on this forum