Continued from here;
In that case it is time to get serious. Dell is unlikely to help here because this appears to be a software problem, not hardware, and likely something that has been installed, or some malware, or similar that has occurred after you received the computer.
So, lets make sure this is not malware. McAfee does a good job for viruses but there is other malware out there that anti-virus scanners do not pick up.
First of all, reboot the computer into Safe Mode With Networking. To do that, restart the computer, and before Windows begins to load start pressing the F8 key gently, once a second. Eventually you should see a list of options. Use the keyboard arrow controls to select "Safe Mode with Networking", then press the Enter key.
Windows will load up, but the display will be larger and not so well defined. There will just be a black Desktop with no background image.
Open your browser and go to the two following links for the free versions of Malwarebytes Anti-malware and SUPERAntiSpyware.
Download those two free anti-malware scanners and save the files to your Desktop.
When done, shutdown and restart the computer and it should restart back into it's Normal Mode.
When Windows is loaded, find those two downloaded files and, one at a time, install MBAM then SAS.
When each one is installed open each and update the malware definitions.
Run each utility's scanners for a full scan, one after the other.
Let each utility find and delete all malware they find.
When they are both done, reboot the computer and try the browsers again.