If you go into Device Manager, you can right click on various components - e.g. network adaptors, audio device, display adaptor - and choose "Update Driver Software... from the pop-up menu.
Even if Gateway don't have Windows 7 drivers, they may have 64-bit Vista drivers which usually do the job OK.
If you download PC Wizard 2010 (or SIW), install and run it, you'll be able to identify all your system components. then you can go directly to the manufacturer of your motherboard and other devices for the latest drivers.
http://www.cpuid.com/pcwizard.phpThere
are websites which provide driver update services, like
http://www.driverguide.com/ but I wouldn't recommend them.