In Windows XP (SP3) you could actually go and view a preview of your webcam through My Computer. I hate to be the bearer of bad news, but Windows 7 does not have any built in web camera software as far as I am aware of.
Why isn’t this a Part of Windows 7
I can’t answer this question, but one can speculate that Microsoft put the role of webcam software provisioning completely to the manufacturer of your specific webcam. After all, up to this date most web camera products are bundled with software that can handle video recording and snapshots. If you simply plugged in the device, Windows 7 in most cases can find the driver, but will NOT download the software package usually bundled with the installation CD. Be sure that you have downloaded the software from your webcam manufacturers website as they often contain ‘Studio’ software which will handle screenshots, recording, and even absurd effects. For example:
Alternatives to Vendor Software
Fortunately, there is plenty of other free webcam software providers. While they may not all be up to notch on quality, I would imagine most would work for general purpose needs.
YawCam – I use this personally, it is not the most friendly software as it brings forward a lot of complexity (but at the gain of features)
ManyCam – Will allow for video effects / webcam server/ screenshots / etc!
Easy Free Web Cam
There are others out there as well but these are the ones that come to mind.
Quick Way to Test
Quickest way to test without installation of software would be to use a website that uses Adobe Flash to show your webcam. This website provides a great tool to view your webcam, as well as to save images from it.
Hope this helps!