|See if the maint book is at HP to start. They do have factory key strokes to light the lamp but not normally to enable video at lcd. |
Most laptops default to internal and don't even have a bios option for external. To be sure look at bios settings.
See also the keyboard. There are contrast and brightness controls normally somewhere. Both may or may not work by design. Try both to lighten.
You can get repair parts but see the cost of new systems. Not much more than the overpriced repair parts you find on auction sites. Not worth the time to hope you order the correct part even.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10