You can most certainly download and organize all of the drivers that you will need. However, you will not be able to do anything with them until you have Windows 7 installed. Windows ships with basic drivers for most devices that will ensure that they are functional enough for you to install drivers that provided by the vendor.
What you can do to save yourself some time is download the Windows7 ISO with Service Pack 1 included and burn that to a DVD. If you buy one from the store it might not have SP1 included. You can use this to trial Windows 7 for 30 days before a product key is required.
Please note that these downloads are provided by Microsoft and are not considered piracy so long as the trial period is not abusedhttp://www.w7forums.com/official-windows-7-sp1-iso-image-downloads-t12325.html