try a few of the suggestions in this article http://support.microsoft.com/kb/324103
also, if you know how, go into bios and check whether you're on AHCI or ATA for your sata port
(AHCI requires you load an extra driver from within the setup so it'd just be easier if it's set to ATA)
(you can then switch back over to AHCI mode after you install using this guide http://www.blah-blah...-s/enable-ahci/
edit: also, what gateway laptop is it, and did it have XP on it originally? i ask because I know for a fact that newer (aka if it had 7 installed originally, not sure about the vista models) gateway laptops (not just gateway for that matter) it's impossible to install XP and below on.