I lost everything! Now what?
This, too, depends on the virus – and how valuable your ‘data’ was. If your data (the files, email addresses or other information) on your computer was not backed up, and you had a ‘simple destructive’ virus, it may be possible to recover at least some of your information. It may not be pretty or very useable when it comes back, but you can often recover significant amounts of data even if the drive has been formatted. There are data-recovery services available at a rather exorbitant rate (if your data means that much to you – it may be worth it), or you can try doing it yourself using software like Recuva.
If you *do* attempt to do it yourself be aware that you should not boot the computer into or onto the ‘lost’ drive, you may inadvertently damage some of the data, since it is no longer protected by virtue of file-system flags indicating that the drive-space where the data currently resides is ‘in use.’ Simply creating a ‘temp’ file for some basic operations, or booting Windows can effectively completely erase some of your data (inevitably the most valuable part, of course!).