CoolWatermark is just an assembly for .NET, so there is no any requirement for hardware if your computer is able to install .NET ©.
But there is some requirements for software eviroment:

1. Microsoft (R) .NET Framework version 1.0.3705 or later installed, SP2 is recommended to install
2. Microsoft (R) Visual Studio .NET (Recommended)
3. Microsoft (R) WINDOWS NT/2K or later (Recommended)