Hi, my computer went dead the other day, as I was trying to connect a new external dvd-rw drive to it. Now it won't turn on at all, not a sound, not a flicker. My engineer friend says its most likely a problem with the PSU, so now I'm looking for a replacement unit. I just wanted to know if there are any compatibility issues with PSU's, or are they universally compatible? Do i need to get an exact wattage/voltage for my computer, or can i just get the most powerful one i find? Thanks for your help.