How to AVERAGEIF with positive, negative and zeroes?

I have a column of data that includes positive numbers, negative numbers and zeroes. I tried =AVERAGEIF(AO2:AO52,"<>0") and =AVERAGEIF(AO2:AO52,"<>0",AO2:AO52)but I get a divide by zero error. If I do =AVERAGEIF(AO2:AO52,">0") I get an average of the positive numbers, and if I do =AVERAGEIF(AO2:AO52,"<0") I get an average of all the negative numbers, but I cant seem to get an average of ALL of the numbers (excluding the zeroes). Does anyone have an idea how to make this work in Excel 2007? Thanks!