Quote Originally Posted by JPR
its going to have to wait until after chistmass apperntly were on a budget. Is it going to hurt the computer if i keep running it the noise dosnt start all the time but sometimes about 5hrs after the computers on and its like a low loud hum i dont know if its the fan or not
I would say that you shouldnt run into problems as long as you dont keep the computer running 24/7. If you want to play it safe, if you start hearing the noise, then you can shut it off.

Also, you may want to look into a program to show you what the computer is running at temp wise inside, they are pretty easy to find, here is the one I use:

SpeedFan - Access temperature sensor in your computer

Its possible, depending on the model XPS, that they have the fans set to run at a slower RPM if the computer isnt running hot, and that they "boost" up to a higher or max RPM when the computer starts getting too warm. The best way to tell is to take down the temp of teh different spots in the computer via that program when it starts making the noise, to see what its running at.