If you want to install Windows 10 on your new computer, then you have to prepare a bootable USB drive using a tool like Rufus. Through this bootable USB drive, you can install Windows 10 on your PC. You have to do the same for other versions like Windows 7 or Windows 8.1 if you want to install them. But this way you would need multiple USB drives or erase the same USB drive again and again. If you want to use the same USB drive for installing multiple versions of Windows without erasing it repeatedly, then you can use the free WinUSB tool that can help you create multi-boot USB drives.
Using this tool you can create not only a USB drive carrying multiple versions of Windows, but you can also include multiple versions and distributions of Linux. Of course, your USB drive must have enough capacity to carry all those installations. If you want three or four operating systems on this multi-boot drive, then you should get a 16 GB USB drive. Needless to mention that a USB 3.0 drive would perform much better.
After attaching the USB drive in your PC, you can launch WinUSB tool and select either an ISO or the DVD drive that carries Windows installation files. You can add more than one Windows versions on this USB drive. And you can reuse the same USB drive to add more operating systems later on.
As you can guess, the more operating systems you add, the more space is needed on the USB drive and the slower is the USB drive creation process. The WinUSB tool uses the popular Grub loader to add so many operating systems on the same USB drive and makes it easy to put installation files for more than one versions of Windows on this multi-boot USB drive.
You can download WinUSB from https://www.winusb.net/.