If you buy a computer from Dell it'll have the Dell Support Center installed and it'll show up every time you start your computer. Just one more piece of cruft on your Dell PC. So here's what to do to disable the Dell Support Center so that it no longer starts running when you start your computer (this should work for either XP or Vista).

Go to Start -> Run and enter msconfig in the box and click the OK button. This should start the System Configuration Utility.

In the System Configuration Utility, click on the Startup tab. Look for the row that contains SupportSoft in it and then uncheck the box for this row. Once you've unchecked the box, click on the Apply button and then the OK button.

This should keep the Dell Support Center from running on your computer.