Hej,
Daniel is right, you gotta figure out why the chip burnt. Most likely your motor requires much more power than the one the ULN2003A can actually handle. I would suggest you go directly to try with HEXMOS switching tecnology (transistors), I recommend you the IRFZ24, (http://www.elfa.se/pdf/71/07117450.pdf). The form-factor should be TO220 (see picture) which allows the connection of a big radiator to disipate power to the air.
Hasta pronto,
/David