I went to start my riding mower for the first time this year and when it started is smoked real bad. I turned it off and checked the oil, it was over filled. I went to drain the oil and discovered it had gas in the oil. It ran fine last year, but I didn't drain the gas out at the end of the season. What could be the problem?

Your carb needle valve has been leaking/dripping all winter. Shut of the fuel line. Drain the gas/oil as completely as you can, even tip the unit to the side to get more out. Fill with cheap oil and crank it or start it for a moment. Drain this oil out and add new good oil. The float and needle valve need to be disassembled and inspected. Repair or replace what you can. The float is bad if you can hear any sloshing inside or it doesn't completely float in gas. Same thing happened to my pressure washer last week. Couldn't do the carb work so now I just shut off the fuel after every use.

Good Answer, But Why Couldn't You Do The Carb Work??

It was my washer and no one was paying me to fix my own stuff. I stayed on the job to make money. I did recently do the carb work. Time is money for me.