they actually did. the inverter...what kind of cost am i lookin at do you think? or should i take it to best buy or should i order the part? is it just called the inverter for the dell inspiron 5150? thanks

I'd be surprised if CompUSA replaced a backlight. If they did and the screen is still dark, the inverter has failed.

If you hook up your laptop to an external monitor and can see the image just fine, it's probably your inverter. I just replaced one in a 5160. Dell has the schematics online showing step by step taking apart your laptop. As screens are different, I first took out the inverter and found a replacement on ebay. It was $48 delivered. There are quite a few screws (about 28-30) by the time you get it dismantled. I just put into paper cups and marked which was which. It works perfectly now. P.S. Shame on CompUSA for not checking the inverter first. I had called them and they wanted $160 to check my inverter to see if it was any good. Obviously it was easier just to order a replacement.