Could any one refer me to a decent image resizing tool ?

Currently, to rescale my own icons I have to use :
- Microsoft's Image Resizer Powertoy to get the icons down to a smaller size
(works in batch, but the aspect ratio often doesn't fit the 64 x 32 required on the Harmony)
- Paint Shop Pro to adjust the Canvas size to fit the 64 x 32 screen without stretching the image (this doesn't seem to work in batch)

There must be some tool out there, which will auto-resize and pad the borders to maintain the aspect ratio ?

Ideally a tool that can take one swipe against batch files would be useful.