What would be the reasons for a cd/dvd rom door not opening when theres no disk is inside?

It could be defective or
the power cable is loose inside, or
the power supply is not providing the power for the CD/DVD drive to operate properly.

Could be anything from the process never reaching execution to the eject button being broken.

You could probably check and make sure its not the Eject button by opening up a music
player such as windows music player and pressing Control + E, I think thats eject.

If not then its probably just a faulty disk drive.

thank you ninyjobs, I actually called hp and opended up the tower and found out that it wasn’t connected properly, you were right on the money. :)