How exactly are you running a network install? Are you trying to run the DVD or ISO from another computer using the currently installed OS? Where did you get Win7?
It's likely an installer read problem since Win7 has all SATA controllers, unless this netbook is old enough to only have IDE. You could try to insert the SATA controller driver at Load Drivers link on that page, but no guarantees.
If you fill in your specs or at least tell us your netbook make/model we can help you more.
Try flash stick install. Easiest method is to install UltraISO trial version, on File tab open ISO, on Bootable tab Write Disk Image, Format, Write. Boot stick under USB or HD's on one-time BIOS Boot Menu, or in BIOS Boot Order menu.