When on minecraft to get DayZ I hit down load either stable or latest 1.64898, hit open or save, then open folder and I get erros message failed to load Main-Class attribute from C:\User .....What do I do?

You need to save the DayZ-Minecraft-1.6.4-8.9.8.jar on your computer then move it to the mods folder in your Minecraft directory. Make sure Minecraft Forge is installed then run Minecraft.