You know.... I would just reinstall everything fresh and clean. Dell has lots of crap out of the box....
My XPS laptop used to be slow as hell too but I cleaned re-install evertying, no virus protection and no nothing... just bunch of regular programs and poker programs...
works like an XPS......
U may have trojan running or basically just be careful where u go on the net...... dont click YES to any pop up that ask you YES or NO.........
Sorry if this may offend you..... just a little advise...........