My computer starts to slow down and the sound starts to crackle at about two and a half hours into use but is fine on a reboot. what is causing this?

When it starts to slow, take the cap off the fuel tank and see if there is a difference. Sounds like the fuel tank has no vent and develops suction and then lacks fuel.

There are so many reasons can cause a Lenovo G560 computer running slow than it used to, it is hard to identify just what might be dragging down your Lenovo's performance, let alone implement the necessary technical adjustments to fix it.

If you want to address the issues more easily, I'll recommend you try a Lenovo speed up software, available here: http://www.speeduplenovo.com/

Best regards!

Go to Control Panel>Large Icon View>Sound>Playback Tab>Right Click The Headset Icon>Properties>Advanced Tab>Change the Default format from CD quality to DVD quality and voila. :D

It sounds like you are having a video card issue. Either that or the computer is running too many programs at once and causing it to run out of ram.

The crackling could be due to a faulty wire or jack connection. If you have any other sound device (e.g. headphones), try connecting that one instead of the Z4 and see whether the crackling disappears (in which case it's the Z4) or not (in which case it's the jack or the computer). Could arguably be an EM or electrical interference, but you'd need a laptop running on batteries to check the second, and trying orienting differently the speakers to try checking the first.

The music slowing down means something's wrong in the computer: the Z4 are purely passive, they can't do anything to the music tempo. Try running an antivirus check or try Task Manager (or Process Explorer) and see whether anything's eating more CPU than it should.

1. The most likely cause of this is dirt/dust in the volume potentiometer. When the set gets warm it starts to crackle. You can try bllowing or sucking the dist out of the set. But the better option is to have the sound module replaced
   

That's most likely a virus that's gotten into your sound device drivers. Try updating/reinstalling them. Try Dell's website or a search engine for exact drivers and how to install them.

Use Internet Explorer to download this file:

http://winhlp.com/tools/resetdma.vbs

Run it.

Reboot system.

Sounds to me like your graphics processor is overheating, or possibly the cpu. Are any of these components new? you may want to make sure that they have proper cooling. On the other hand if its a few years old, may jus need to replace the overheating component.

turn it off for an hour see if that works could be overheating