Out of curiosity is your system a store bought OEM system from a major manufacturer (Dell, HP, IBM, etc.) or something put together from components?
Is the system functional/bootable now?
Where (easily enough) do you expect to download the Windows 7 installation file?
Once Windows has been installed you might be able to get the system on the Internet where you can download device drivers and you might not be able to get on the Internet.
If you know a few details of the hardware you could from a working system download the Ethernet/LAN driver beforehand and save it on something like a USB thumb drive for when you need it, then when you get the system on the Internet you can get the other drivers you need from the hardware manufacturers WWW site (never from Windows Update).
Or when Windows is installed download the (at least) the network drivers to a working system, copy it to a USB thumb drive and use Sneakernet to apply it to the new installation.
If the system is bootable now do this so we can see what you have:
What is your system make and model or is it something assembled from separately purchased components?
If the system is a Dell what is the Service Tag Number?
If the system is an HP what is the serial number?
If the system is an Toshiba what is the serial number?
Click Start, Run and in the box enter:
Click OK, and when the System Summary info appears, click Edit, Select All (Ctrl-A), Copy (Ctrl-C) and then paste (Ctrl-V) the information back here in your next reply.
There will be some personal information (like System Name and User Name), and whatever appears to be private information to you, just delete it from the pasted information.