These are to stop data mining bots from creating accounts, they will scan forums such as this one, log information and e-mail addresses then the owners sell this info. They also post advertisements in mass spam form.
These among others, are some reason for these extra security steps. You can request a new image until its one you can clearly read, you can try the text, or you can maybe blow up the size [hold control key down and scroll mouse wheel up, outside of the information entry box] if that helps,. all you can really do, any software that di it for you would defeat the purpose, be quickly found out, and have the system altered to counter that.