Others may use Irfan.
I've been living in the stone age. There's a relatively new 100 percent free, 100 percent spyware/adware free viewer called Fast Stone that just plain rocks.
It's as fast or faster than ACDSee classic but it has a super slick user interface that has tons of useful things like resizing, simple editing, cropping, batch operations including renaming, resizing, etc. It only takes a few minutes using it to realize that it kicks the holy shit out of ACDSee classic while retaining all the speed.
Even better is the developer continuously updates it.
I know what you're thinking...this can't possibly a better image viewer than Copernic is a desktop search engine but I'd put it on the same level. You're also thinking, "my image viewer works just fine...I don't need a new one" Of course you're thinking that. Image viewing is a pretty brain dead activity for the most part but for the love of christ, give this one a try. It's small, it's fast, yet it packs some serious functionality into an extremely slick full screen view mode.
Fast Stone for the win!
http://www.faststone.org/FSViewerDetail.htm
BTW, you can't see how slick the UI is by the single non full screen picture in the link. That pic looks like any other image browser you've seen. You need to experience the full screen mode and it's side screen pop menus. Download it and give it a whirl. It's worth it. Try the 2.0 beta 0401 released April 1st. I've been using it and it's stable.
I used to have to switch to Microsoft Image editor to do my resizing, etc for posting the comics covers, and making small image edits but this Fast Stone is an unholy combo of speed image viewing and ultra quick access to the most useful of editing and batch functions plus some kick ass ways to sort your images for viewing that ACDSee never dreamed of.(I hate how you can only view numberically/alphabetically wiuth ACDSee Classic)
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