Wordpress - Searching multiple custom post types and pages

change

<input type="hidden" name="post_type" value="software" />

to

<input type="hidden" name="post_type[]" value="software" />
<input type="hidden" name="post_type[]" value="books" />

i have to run but this should work , just add as many hidden fields as you need for each post type

You could do it like this to switch between a singular set type and any..

<input type="hidden" name="post_type" value="software" />
<label for="post_type">Search all</label>
<input type="checkbox" name="post_type" value="any" />

Unchecked searches your specific type, checked sets the post type to any..