Windows xp machine slows down when connecting to the internet through dialup

I have a windows xp machine that works fine when I am not using dial up, but once connected through dialup the machine takes serveral minutes to do anything. Just bringing up a browser will take up to 10 minutes. However the very second I disconnect from the internet everything goes back to normal and I can use my machine again. I have also discovered that if I open the browser first then connect to the internet, I can surf, but I can't bring up another window or open any other programs without waiting for serveral minutes. Has anyone encountered this issue. I have checked in msconfig and looked at the task manager to see if anything looks suspicious, but I haven't found anything. I have installed avg spybot and will soon install superantispyware to see if it can find anything. Any help would be greatly appreciated. I am thinking about unistalling and reinstalling the networking/dialup components to see if that would help. Any thoughts.