Are you running IIS or Apache on the Windows Server? If Apache, then yes, you can use .htaccess files.
The Referer (or properly spelled, Referrer -- apache has spelled it wrong all these years and it has sort of stuck), is the site which is requesting the image. The Browser passes this info along when it does the request. In the above, you would replace example.com with your domain name to allow your site to display images properly. Places that have hotlinked would then be served the nohotlink image.
A while back Raymor, Swedguy and a few other people banged on this as being about the best optimized, most complete .htaccess rule.
http://www.greenguysboard.com/board/...em#faq_hotlink
If you are running IIS, then you need to get an ISAPI filter to do referral protection, and I remember one product being Coldlink which did a programmatic hash on the url path of images that needed to be protected.