Inspiron N5110's touchpad does not work correctly???

Hello, I'm using inspiron N5510 and I installed full software driver for my laptop.

My problem is that the mouse icon can't move correctly sometime it doesn't move or drag from left to right screen  when I use touchpad - with power connecting even thought my touchpad dell icon in the taskbar shows correct the place I touch but it's ok when I unplug power line and use battery.

In addition, when I listen to music, play games etc. the screen motion will be stopped for about a second and the sound stays the same at the time the screen  stops and it happens for about every 5-6 minutes in spite of using light softwares like WMP and the GPU temp is appr. 36-50oC.

Does anyone know what wrong with my computer, which parts are having problems ?