Upon powering up the computer, the light on front comes on, the CD/DVD drive runs, I can feel the HD turning, but the display remains black, no display at all. After a some seconds, the computer beeps 4 times, hesitates, and beeps 4 times and continues this pattern until I turn off the power. I put an UBUNTU live CD into the CD/DVD drive, and the sequence repeats as before. I remove the disk from the CD/DVD drive, and repeat: same thing.
Some months ago, I salvaged the original HD from this computer due to it failing. I retrieved some priceless photos my niece took in Afghanistan, and I replaced the HD with an approved new one. I also added RAM to max out the motherboard. I installed UBUNTU Studio on the new HD, gave it to my daughter, and the computer has performed flawlessly for almost a year. Two days ago, lines started appearing on the display, according to my daughter, and yesterday it ended up in the state I described above.
What are the steps to repairing the computer? I have more than average knowledge with computers, have repaired, upgraded, and built some systems, but I hardly call myself a technician. So, instructions suitable to a layman are encouraged. Thanks.