If you will be 18 on Oct 24th 2008 can you vote in 2008 presidential Election?

Yes, if you have registered in time according to your state's laws. All states have some kind of voter registration deadline. If your state's deadline is before your birthday, you can usually register before hand, because you "are or will be 18 years of age or older on or before the election day" or some such provision. The election day is November 4th.