Several users have reported an issue in which installation of Windows 7 fails, freezing on the “Completing Installation” phase.
Disconnect external/internal devices The most common fix for this issue is to disconnect all external USB devices, excluding the keyboard and mouse, prior to installation. If installation still fails, try disconnecting the keyboard and mouse right before the freezing phase occurs.
Some users have also reported that they needed to disconnect internal third-party video cards or secondary (dual) monitors before installation would occur properly. The bottom line: get your system as close to bare-bones as possible prior to installation.
Turn on SATA AHCI Enter your system’s BIOS mode. This is accomplished by pressing a specific key repeatedly as soon as your computer is turned on (or right after it is restarted). For many computers, the key is F8, but it may be F1, F2, F10, the Delete (del) key or the Escape (ESC) key. Consult your computer or motherboard’s manual or try different keys until you find the right one.
Next check your HDD or storage settings–it may be set to “legacy device.” Change it to native SATA mode (SATA AHCI).