The Biblical picture of pre-destination is a complex one with some passages suggesting that it is true and others suggesting the reverse. In light of this my personal view is that God may well known what we are going to do, but that doesnt mean that he has pre-determined what we are doing.This example may help, I know what my friend will do in a certain situation, s/he knows what we are going to do even before we do it.
Passages:
Pre-destination: Romans 8:28-30; Ephesians 1:11-12; Proverbs 16:4 (among others)
Free-will: 2 Peter 3:9; Luke 11:9-10; 1 Timothy 2:4; Deuteronomy 30:11-19 (among others)