I have an old HP Pavilion DM3 1030 laptop and I'm trying to replace the LCD inverter on it. Being an old model, I can't find the exact part. Can I use an inverter board from a different HP laptop of comparable LCD screen size?
No, LCD screen size is not a good indication of compatibility. Within the same company (HP, Dell, etc) they use different LCD manufactors (Sharp, Samsung, etc). They potentially could have different plug sockets and power requirements for the same size screens on different models. You need to get the part numbers of each (the inverter and LCD) and search for compatibility that way. Probably easier to buy a parts laptop with a dead motherboard etc, and replace both. BTW - are you sure its not the LCD lamp?