I have a big problem with dual-boot. I have three partitions: C: 146 GB capacity, 73 GB free D: 146 GB capacity, 97 GB free E: 172 GB capacity, 126 GB free So, on C: drive I have Windows 7 Ultimate 32-bit already installed, but yesterday I tried to set dual-boot so I can run both Windows 7 Ultimate and Windows 8.1 Pro. But, I installed Windows 8.1 Pro on D: drive (DVD which I burned with Windows 7 USB/DVD Download Tool using ISO en_windows_8_1_x86_dvd_2707392.iso) without problems and I activated it. But now I cannot manage Windows 7 to work, so instead of this, Windows 8.1 Pro is now default OS, instead of choosing OS on Startup. And now, D: drive is now C: drive, and C: drive (Windows 7 drive) is now E: drive. In Disk Management, C: drive is marked as boot drive, but E: drive isn't. If I mark E: drive as active, I cannot run any Windows. So, how to set dual-boot so I can choose which system to run? My specs of laptop: Intel Pentium P6200 2.13 GHz Intel HD Graphics Pentium P6200 3 GB RAM DDR3 500 GB HDD Windows 7 Ultimate x86 and Windows 8.1 Pro x86 Thank you in advance.