I recently repaired a Sony Vaio Laptop. I added RAM, installed a new battery and purchased a new power supply. The problem the owner of this laptop was having was that it wouldn't boot. After I performed the above repairs and upgrades I kept the laptop for several days, ran it on the battery until the battery ran down, recharged the battery, ran the system for hours on end, rebooted it several time, shut it down periodically, closed the lid to put it in standby, brought it out of standby etc. The only time I had a problem was when I tried to run it from just the power supply and I plugged in the old one. Once I plugged in the new power supply it fired up again. The problem is, I returned it to the owner and she took it home and now it won't boot. The power indicator and battery light flash and go off but the computer does not boot. Any ideas what the problem could be? Any suggestions as to what I should be looking at to solve this problem.