Quite sure that last time you had a different sketch. You're missing the setup() function. Add the following to your sketch and see if it compiles.
void setup()
{
}
Do not upload it as the above setup() is incomplete.
Your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project 
See About the IDE 1.x category.