Start by installing Windows 98, I should say.
If I remember correctly Photoshop 4 (from 1996) was a 16-Bit application.
Then it cannot be run on a Windows 10/64Bit machine.
It MAY run on a Windows 7 / 32 Bit system - compatibility mode or on a virtual machine.
Read this discussion: Is it possible to run a 16-bit program on Windows 10 64-bit - Microsoft Community
PS: Or did you mean Photoshop CS 4?
The "I insist on running Photoshop 4 on Windows 10" method:
- Download and install a virtual machine, such as Oracle VirtualBox Downloads – Oracle VM VirtualBox
- Create a new virtual machine in VirtualBox, and choose Windows 98.
- Install Windows 98 in your virtual machine, and when finished, start Win98 and install Photoshop 4.
Photoshop 4 will not run natively on Windows 10.
The simple methods include:
- Subscribe to rent Photoshop CC, or if you dislike to or cannot rent your software:
- Purchase a license of Photoshop Elements (perhaps with ElementsXXL) or
- Purchase a license of either PhotoLine or Affinity Photo, or
- No money? Install GIMP