Before you go that far,

Is Windows up to date on critical patches, is your antivirus software and your firewall up to date and running, and have you scanned for spyware (www.lavasoftusa.com)?

KNOWHATODO.

To find the Dell reinstall guide, that's specific to your system, go here and enter the service tag.

http://support.dell.com/support/topics/global.aspx/support/software_reinstall/en/index?c=us&cs=19&l=en&s=dhs

Bev.