Video, sound lag, spikes

[cyborg321]

Hello, so I have a problem with my computer. When I am watching a video or listening to a song or playing a video game I get lag.
SPECS:
Intel Pentium dual core e6500 2.93 ghz
GTX 650 Gygabite 1gb edition GPU
550w psu

 

[kenrivers]

How much RAM do you have?

 

[cyborg321]

How much RAM do you have?

I have 4gb 1333mhz ddr3