It is a free web site that install a certified plugin on your browser and list missing and outdated drivers and point links to download then.
- Works on Firefox, IE, Chrome, Safari and Opera
- Require Flash Player installed
- Detection for 32-bit and 64-bit system
- Windows 2000 and XP SP1 or above
There is also a offline detection tool witch you run offline it generates a result file, and you have to use another computer with internet to upload it to get the drivers.
There are tons of sites that claim to do the same, but most of then are paid services, and just give you a demo, and most don't let you actually download the drives unless you pay.
P.S. I do not work for then or anything like that, I use it for my personal use.