This could well be a BIOS settings issue. Please go into the BIOS setup and try various combinations of boot and HDD settings.
When you installed Windows the first time, do you remember the settings? UEFI or legacy boot? IDE, AHCI or RAID? These settings tell the BIOS how to access your HDD. If they are not the same as they were when you installed Windows, it won't find your data. So try changing the settings one by one until you get it right. There are some 6 combinations to try.
Worst case, you set the boot configuration you want, and install Windows again from a DVD or USB pen drive, delete all the existing partitions on your HDD, and let Windows do its thing. It will create the partitions needed automatically.
Reinstall the BIOS version 99 using the recovery method. Use the minimum configuration, using motherboard, processor and 1 memory stick.
Instructions for Recovery BIOS Update
Desktop Boards — Instructions for Recovery BIOS Update