Whenever I click on the switch user icon, my computer reboots. Is there a setting I can click on to fix this problem?

Whats your service pack? Are you sure that fast user switching is enabled?
Go into the control panel, click on user accounts, & then click on "change the way users log on & off." Make sure that both of the check boxes are checked. If either are greyed out then a program or drivers might be blocking that. I had that happen this last summer with the drivers for a netgear adapter (actually it was the program that came with the drivers). I was finally told from a senior tech that it was disabled for security reasons & that there wasn't anything that I could do about it. If you have a netgear wirleess adapter then the same will apply to you, if not then another program could be blocking it.
If both are checked, go back to control panel, click on administrative tools, click on services, & then find "Fast User Switching Compatibility" & double click on it. Make sure the startup type is automatic, & if it isn't started click on the start button.
If it is enabled in services & under user account control then there is a way to switch using a hot key, which would be the windows key + l (for lock) [these have to be pressed at the same time or one must be pressed while you are holding down the other]. You will then get the welcome page & should be able to choose another user, however this can only be done if fast user switching is enabled.
I've got to admit I've never heard of this.