Thanks people! Here is the finished code for those who are interested:

Code:
#include <acknex.h>
#include <windows.h> 

STRING* comp = "#128";

void getComputerName()
{
    char buffer [128];
    long size = 128;

    memset(buffer, 0, size);
    
    if(GetComputerName(buffer, &size))
    {
         str_cpy(comp, buffer);
    }
    else
    {
         str_cpy(comp, "Couldn't get the computer name");
    }
    
    error(comp);
}

void main()
{
  getComputerName();
}