I hate the Windows XP image viewer. Its not customizable in the least bit, and even worse sometimes the damn thing crashes on me. Of course I only use it when I'm on other people's computers though, because I don't run Windows.
Personally, I use GQView. Its the best image viewer I've ever used and I never once had an issue with it. Here are some links:
Homepage
Screenshots
Currently its only available for Linux, so if you are using another O/S too bad but you're missing out.