This is to clarify a little bit more. If you use a Microsoft USB Operating System Convert Utility or something like MSI Smart Tool (which add drivers so Win7 can work on Ryzen CPU), they will not work unless you have an 8GB USB stick. However, you can create an ISO file (with utility of your choice) of a genuine Win7 Pro DVD, which comes out to 3.2GB, then use a USB Boot Installer like WinDiskImager to install a bootable USB stick with that ISO image. You can use a 4GB stick (which is slightly smaller than 4GB) to make an installable USB stick. You can do the same with Win10/11 OS with a 6GB stick. I just did this with a Ryzen 5 motherboard I had in my shed with an old Win7 Pro disk I found in a drawer.