i have a dual boot system with vista ultimate and XP pro sp2 and when using vista i have not experienced this problem, i would do as everyone else is saying, check the task manager also, since the computer is from dell, go start>all programs>accessories>run and type msconfig in the startup tab you will see all the programs that start up with your computer, disable what you don't need and leave the few Microsoft ones post back with anyones you have a question about and then restart.
edit: 1st post