Formatting is easy - it's the rebuilding that takes the time. Do some research and planning before you proceed. Make sure you know every step you are going to have to take to rebuild before you reformat.
First most important step is to make a backup of everything to a completely different drive. Make sure you know how to restore the data AFTER the format. You will also want all your Outlook/Outlook Express data. Read up on how to do that in the help system. Also, make sure you save your "Favorites" folder. If there are other people using your computer, make sure you save their data too.
Make sure you have the install disks for all your hardware and software, and plan to download the latest versions after the system load.
But more important still, is that you avoid getting reconnected to the internet as long as possible. In fact, pull the cable plug so that you cannot accidentally connect until you want to connect. Personally, I don't even let the Windows install make the first connection. I put that off untill later - after I have installed my antivirus and firewall software. You don't want to allow the vultures to get into your computer before you do.
Install a firewall and antivirus and run a scan. Then connect only long enough to down the latest version of the software and virus images. Disconnect immediately while you configure that, and run a scan.
Then, connect only long enough to download the latest version of your operating system. Then disconnect again until you have things configured for maximum protection.
Connect again to get the latest versions of your hardware drivers. Then, disconnect again.
Put off permanently connecting until you think you have all your defenses up and running as best you can.
Then, go about the business of installing each piece of software and downloading the latest versions.
Finally, restore your data from your backup.
Safety from the internet is most important. Be careful, and good luck.
Chuck