While iam installing with usb. It says "A required CD/DVD drive device driver is missing". Please help
Are you using Rufus to image the USB device?
what is the meaning of USB 3.0 ?
Most modern Laptops with INTEL chipsets do not have a native USB 2.0 controller anymore. The only USB 2.0 is found to be usually a Realtek as part of the SD Reader I/O. Windows 7 was released before USB 3.0 was finalized, so therefore it has no basic USB 3.0 ability.
All the USB ports will work in BIOS mode, however, during installation, when the BIOS hands off control to the Operating System being Windows 7, which mind you only has built in drivers for INTEL USB 2.0; a missing device error will occur when installing from a USB device. This error basically will have the Operating System (Windows 7) not being able to gain control over the Realtek USB 2.0 or the Intel USB 3.0, as it's database lacks those drivers.
This version that The RAIN compiled has the USB 3.0 Drivers slipstreamed (integrated) into the installation. So, during installation from a USB device, when the Operating System takes control of the hardware from the BIOS, it will be able to continue. Mind you it's important that your USB thumb drive is plugged into the Blue USB 3.0 ports for this to work.