Hello,
You may need to upgrade your hard drive to be able to install Windows 10. Here are the hardware and system requirements needed based on Microsoft for Windows 10;
Processor:
1 gigahertz (GHz) or faster processor or SoC
RAM:
1 gigabyte (GB) for 32-bit or 2 GB for 64-bit
Hard disk space:
16 GB free space available for 32-bit OS 20 GB free space available for 64-bit OS
Graphics card:
DirectX 9 or later with WDDM 1.0 driver
Display:
800x600