Trying to install Windows 7 on a Gateway M685-E, but no hard drives are found?

I'm not a computer techie, so please bear with me - but I've had a bunch of problems with my computer, so I'm having to reinstall Windows. I have Windows XP professional, but my friend is trying to upgrade me to Windows 7. My computer can hold it, so it's nothing like that, but I have this problem whether I'm trying to install Windows 7 or trying to reinstall Windows XP. I've downloaded the drivers from Gateway's website, but it still won't let me download to them, which is what my friend told me it needs to do - any help? Thanks!