Download Microsoft Security Essentials and do a full system scan. http://www.microsoft.com/security_essentials/
Also as suggested, get Malwarebytes and also run a full system scan.
As stated above, some sites do disable the R click save function.
Instead of R Click copy, try just dragging the image from the browser to the desktop, that works in most cases.
Also, if the problem began recently, you can try a system restore as suggested. If you know when the problem began and you are able to, restore your system to a time before the problem.