1. It sounds like the DPI setting is set too high. I personally CANNOT STAND the high DPU settings Dell uses, but I don't blame them... cause I am sure 3 billion called when they bought high res screens and whines and complained: "I can't read the fonts... blah blah." Goto the display properties --> settings --> advanced --> general and set the DPI to 96dpi.

2. Try installing I8KfanGUI which will give you more control over the fans and monitor the temps. The computer is propably forcing the CPU into a slower speed cause of temps and it gets "locked" at the lower speed.