Some kids played around on a friend's computer. MalwareBytes eliminated nine problems. Now he has two problems that I cannot find. One is that there is a constant "Uh Oh" sound coming from his speakers at random times. I've tried to go through all of the wave files on his computer to find the file, but I have not yet been successful. Presumably some adware renamed one of the standard sound files, but I cannot correlate the frequency of the sound with Click or Navigation. (Windows Media Player, Media Player Classic, VLC, and Adobe Audition will not play some of the sound files although Windows will.) The second problem is that the computer periodically goes to a black screen. Hibernation is not enable, the screen saver is disabled, and the display mode is set to Presentation (always on.) Normally I'd be suspicious of a hardware problem, but this issue did not start until the kids played with the computer. combofix.exe did not find a rootkit. MalwareBytes comes up clean. Where to look next?