IrfanView. Freeware for private use. Not perfect, but about 80-90% of the pictures seemed to work when I tested it.
Use: File - Batch Conversion/Rename. Look at the help (F1) for details, but you can do a bunch of basic convertion stuff. Make sure to add all the files, have an output folder, and use the advanced options with preserve aspect ratio checked.
Afterwards, check through the files and make sure they were all converted. If a file wasn't for some reason, you can convert it by hand or try feeding it through the batch converter again.
Other graphic apps do this too.
BTW, I think you mean to shrink the images to a max 2" x 2" size, right?
If you want to stretch them bigger, I'm with howard and I don't advise it.