Based on the problems you were having in your earlier post, I would suspect either the video card, or video drivers (the fact that you can't get a display upon boot makes me suspect the former.) If you have one available, I would swap out for another video card. If you have on board video, just install a PCI video card and use that instead. If you still have the issues with no video, then look into finding and installing the correct video codec. You can use a program, such as
gspot to identify the codec (I prefer this to simply downloading a codec pack, which adds a lot of unnecessary items.) Another way to go about doing this, would be to use a media player that comes with built in support for a wide range of formats (such as
VLC).But if all else fails you can always attempt to do a clean re-install.
As for the optical drive, I would first download the latest drivers from HP's (or the manufacturers) web site. If that still doesn't work, see if there is a firmware update avilaible. If that doesn't work, then open the case and make sure the IDE cable is seated into the drive and main board. If that still doesn't fix it, you may want to consider replacing the drive.
Jam it back in, in the dark.