Dell Dimension 9200 LGA Swap

I didnt know where to post this as there was not a section for the dimensions as the production is ended but anyway I recently did a LGA 775 to 771 on my dell dimension 9200 and everytime I boot it with the LGA 771 cpu it just gives me the numbers 1,3,4 and I tried to do a custom bios for the cpu but I couldn't load the rom into the editing software is there something that can fix this?