I can recommend Lupas Rename 2000 (long discontinued, but with the greatest amount of options I have seen so far on a self explaining screen).
Rename whatever you want to whatever you want with preview of results, undo and anything else.
Another great program to find, sort, rename and almost anything else is HFT (Handy File Tool). Lets you - for example - collect 125 files from 89 directories and do things to them like moving them to ONE new directory, rename or delete them and so on.
And yes, I still have to find a feature IrfanView doesn't have.