I don't know what version of PSP you have, but there are two ways to do it.

One is to use the cropping tool. That's the way you're supposed to do it.

The other is to use the selection tool (you have to specifically select "rectangle" as opposed to another shape in later versions of PSP), and most importantly make sure antialiasing and feathering are off, then go image/crop to selection.

Do that 301 times. I don't know a way for it to happen automatically.

There is a crapload of other stuff you can do for preserving those images, including fixing up their color fade. The question is, do you want to perfectly preserve them as-is, or are you doing a RESTORATION?

Incidentally, have a look at these. Amazing:

http://www.loc.gov/exhibits/boundforglory/glory-exhibit.html

Some of those have faded considerably, and the latest version of Paint Shop has a Color Balance tool that automatically fixes them and makes them look like they were taken yesterday.