Our windows media and real player has a vibrating sound when we play it.
What is causing it?? This is an OEM system..
We have Windows XP and a Compaq Presario

How much RAM do you have and are you running both of them at the same time or are their any other applications opened too?
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I have 1.0GB Memory and 250GB HD, and a 3500+ AMD Athlon 64 processor, OEM - Windows XP pre-installed, Compaq Presario.
We checked to make sure if any other player was playing. Then I had to turn it off and start over. Sometimes my mouse freezes up and I have to turn it off and start over.. Could it because I have too many windows opened up 3-5??

The opened windows have nothing to do with that...first possible issue may be that your hard drive has the DMA disabled, you can check it in the Device Manager>IDE/ATA Atapi Controllers>Primary IDE Channel.

Since I think that the above event has few chances to occur, you can try the following:

1.Update all your Windows Media codecs, Directx and the sound drivers

2.Try another player, for example VLC -> http://www.videolan.org/

3.Make sure you don't have any disk defragmenter or other aplication that puts a lot of load on the hdd running in the background

Try these and let us know about the outcome.

I had to look up what DMA is. Then I found Device Manager. dma-ide/ata is enabled. It looks like I have the latest updates so far. Thanks for your help.

Check if you have Soundman on your pc, it's a program which I have sofar automatically had on every Windows XP. There you can enable different profiles, check if any of those are enabled and if they are disable them.

Where is the sound coming from? Sound card+ Speakers? Onboard Sound+Speakers? Or with headphones?
Front Audio? Back Audio? headphones plugged into Speakers?

Whatever we tried didn't fix the problem. I also contacted HP the OEM Manufacturer of the 3 1/2 mos. old computer. Then we noticed that the Media center was missing too. (Microsoft Windows XP Media Center
Edition 2005.) After trying more stuff = They had us do a System Recovery. That fixed it. What a pain.
THANK YOU ALL for all your help. No One knows what or why it happened.