I have used Irfanview, but found it a little clumsy to use. Thumbs Plus is good. ACDSee is great. Most of these programs divide the application window into three panels to show 1) a directory tree of your hard-drive; 2) a thumbnail view of all images in a particular folder; and 3) a large view of the selected thumbnail image. Double-click any thumbnail, and it displays fullsize, you can page-up/down to scroll through all images, and these programs can even display the contents of zip files without unzipping them, as if they were a sub-directory full of images.
Another neat program is Lview. It is much smaller program, a few editing features (crop, rotate etc) and not much else. But is great for older/slower machines, or if you just want something quick and easy.
Once you associate .jpg extensions/file-types with any of these programs, it should launch the program and display the image whenever you double-click the image in windows explorer, or you can instruct programs such as mIRC to automatically launch and open images sent to you with this application.
There are dozens of other image viewers. Just do a search for any of these in the Graphics/Image viewing/editing section of popular freeware/shareware sites (eg,
TuCows.com,
c|net shareware.com,
c|net downloads.com etc), to find one that suits you. Many of these programs have been through various incarnations of freeware, shareware, and commercial release, so if you don't absolutely need the lastest version, search through the cover CDs of old computer/web related magazines for an older version.
Of course, you can always use good old Internet Explorer to view .jpg files if you have nothing else. Just Ctrl-O (File>Open) and browse your local hard-drive for the image you want to view.
