How to reinstall Windows and get everything back to normal?

That disk should work. More than likely that is a recovery disk (since I'm guessing the computer is not brand new) so just pop it in and when the BIOS (black screen that loads Dell) comes up at the beginning there could be something that will come up to load Boot Disk. If not press whatever key to look at system settings or options and then a list of options will come up and one should be to boot from CD-ROM. Click on that and follow the instructions. All your files might disappear. Also if you know when you got the virus you can go under system restore in the accessories folder on the start menu under system tools and you can almost travel back in time in order to have to computer the way it was before the problem. Usually worm viruses don't allow you to do this, so it might work. But if you have to use the disk just follow the step by step instructions.