Dummy IP Address/Lost Internet Connection/Slow Access

Help!!!  About 2 weeks ago I lost my Internet connection.  I have a cable modem and my first instinct was to call their help desk. Response: I had a dummy IP Address and needed to contact Dell to get the problem fixed.  Called Dell and ended up re-installing XP program.   What's bugging be the most is that since this has all started my system has gotten really slow when loading "personal settings".  It doesn't matter whose account we go into. 

I have a Dimension 4600.

Thanks....