Hi,
This is being caused by the file atikmpag.sys
This file relates to your AMD graphics driver.
Therefore you need to install a more stable version of the driver which you can source from either Dell's support site or direct from AMD.
There are 2 drivers on Dell's site depending on what AMD GPU you have (Windows 7 64bit)
AMD Radeon HD 7670M (Release date - 06/02/2013)
www.dell.com/.../inspiron-15-3521
AMD Radeon HD 8730M (Release date - 06/02/2013)
www.dell.com/.../inspiron-15-3521
This is the link to the latest driver from AMD (Release date 5/29/2013)