Thank you for visiting the HP Forums! A great place where you can find solutions for your issues with help from the community! I came across your post and wanted to assist you. I understand you are having issues with the computer won't boot and extremely dim display on HP notebook. Don't worry as I have a few suggestions which should help you resolve this issue.
To provide you with an accurate solution, I'll need a few more details:
(Ensure you do not share any of your personal information such as serial, phone number, email ID, etc...).
Have you recently made any software or hardware changes on the PC before the issue started?
Did it happen after a recent software update?
Have you tried to check in the Bios? If the screen brightness is dim, then it's a possible hardware issue.
In the meantime, let's try these steps here:
Perform a Hard reset on the notebook: Many startup errors and other problems can be resolved by decreasing the amount of power stored in hardware components. Decreasing stored power is sometimes referred to as a "Hard Reset". Use the following steps to perform a hard reset on a computer:
Step 1: Restart the notebook with AC power
Step 2: Check the display before Windows Opens
Step 3: Adjust the LCD brightness using the function keys
Step 4: Update the BIOS and graphics drivers
In some cases, a dim display might be caused by an outdated BIOS or graphics driver. Select from the following options below to update the BIOS and graphics driver on your computer:
If the display is still dim after updating the BIOS and graphics driver and as you mentioned it works fine on an alternate product, it's more likely a hardware failure within the LCD,
If you have followed the steps suggested and still having the issue. I would personally suggest this could be a possible hardware failure. I would recommend you contact our HP phone support for further assistance.