Windows 7 compressed ISO around 900 MB typically involves using unofficial "Lite" or "Super Lite" editions. Standard official Windows 7 ISOs are much larger—approximately 2.34 GB for 32-bit 3.10 GB for 64-bit Microsoft Community Hub Highly Compressed & "Lite" ISO Options
Use a tool like Rufus to flash the 900MB ISO onto a USB drive. windows 7 compressed iso 900 mb fixed