As some anecdotal evidence against your point, I've installed Windows 7 on three different systems from a USB stick and all three had the same issue: the instal

As some anecdotal evidence against your point, I've installed Windows 7 on three different systems from a USB stick and all three had the same issue: the installer is unable to see the hard disk while the USB drive is plugged in. From searching around the first time I had the issue it seems like this is well known but there isn't really any effort to fix it. Only solution I was able to use was to format the hard disk NTFS and copy USB drive contents to the disk and boot without the USB. I've also installed a couple different Linux distros from USB and never had any issues (with the install...).