Urgent: How do I REthumbnail the Images?

[Fuztug]

hello,

I have a big problem:
I want mine Images rethumbed. Cause I have various sizes. So I want to unite it all to ONE size. The Problem is, some pictueres are below, and some above my wished size. So the pics which are above my wished size could be resized, but these which are below can't be.

Any1 know how to manage it`?

Thx,
Fuztug!

[Apollo13]

well just a dirty way. U can set in the im tag. a fixed width and height. But than all images have the same width and height and this i think doesn't look very nice