It seems more like a hardware issue than a software issue. Hold off on buying any software for now.
If your speakers are making a buzzing sound, it might be a problem with some of your cables, check that none of them are peeled. It can also mean that you have something with a magnet close to the computer area. Magnetism can mess with everything, form the speakers, to the modem, it can also screw up the data on the hard disc.
Make sure your power outlets are properly grounded, or if you have a surge supressor or a multi plug, check that it's working properly. Try moving the speakers away form the monitor and also the phone, if you have it on the same desk.
Hope you can solve this without spending too much money...