This program was developed by a student, Markham Bey, who has long since gone on to bigger things, but maintains this, his most popular program.
Link; http://www.irfanview.ca/
I set it up as my default image viewer because it's so damn fast. I shudder when I see people with I.E. or Photoshop as their default; talk about overkill!
And as tiny and super-fast as it is, it can do all the basic editing, incuding batch processing (converting a bunch of bmp's to jpg's, etc), text overlays, cropping, etc etc.
I even use it at work; if you just want to make sure a buch of renders turned out the way you expected, nothing lets you breeze through them faster.
... I hope this doesn't look like an advertisement
I just have always thought this is by far and away the best way to quickly view images.