Originally Answered: How to fix my computer from lagging and video/sound from lagging and stuttering?
Try using a different set of speakers. (pretty easy test) If the problem still exists, try a different sound card. (cheap to replace). Adding more RAM (memory sticks inside) could help. If you are listening to music online, make sure you aren't downloading anything else while you are doing it, and that other people aren't downloading if there are multiple computers hooked up to the internet.
Don't jump right to the "IT"S A VIRUS" answer that is popular with people that don't even know what a virus is. If it was a virus, your hard drive would be full. All a virus does is replicate itself to take up disk space. Period.. that is it, nothing else. If you really really really want to be sure you don't have MALWARE.. (trojan, key logger, spyware, worm) also run CCleaner. Between your antivirus, malwarebytes and ccleaner, those will catch pretty much anything that could be infecting your computer, if they say your computer is clean, it IS CLEAN. Do a disk defrag, take your music and video files off your pc and put them on dvds. A really simple way to look at this is.. if you want a Coke, is it faster to go to the refrigerator and get one, or walk to the supermarket, search through all the aisles, find Coke, then bring it home and drink it? A hard drive is quite similar, the shorter the distance it has to go to look for the info you need, the faster it is. After you take the junk and stuff off the disk, defragment it. (compacts the files and free space so the computer doesn't have to go looking for bits and pieces of files all over the place)
I've listed these in the order you should check, first to last. Always troubleshoot the easiest and cheapest solutions first. That way, you don't spend $75 or so to have a non-existant virus removed, when it was just a piece of debris inside your speaker case, vibrating against the case and the actual speaker. BTW, if you play your music loud, this can cause that diaphragm to tear or stretch, which of course will distort the sound.