Legendary country singer Glen Campbell,75, has told People magazine that he has been diagnosed with Alzheimer's Disease. Campbell is still able to perform and will hold a series of farewell concerts. He wanted his fans to know about his condition because he didn't want any missteps during the concerts to be construed as a lack of professionalism. Campbell hit the big time in the 1960s crossing over to the pop charts with many hit songs. He also enjoyed a successful, but brief, acting career highlighted by his co-starring role with John Wayne in the the original 1969 version of True Grit. The Oscar-nominated theme song to the film was warbled by Campbell and became a major hit on the charts. For more click here