Could Voting Machines Steal the Election?

In the year 2000, "hanging chads" on Florida's paper ballots put the presidential election in doubt. Two years later, Congress passed the Help America Vote Act, or HAVA, which provided federal subsidies for states to buy electronic voting machines that don't use paper at all. Dispute is raging over what it could mean for the integrity of next week's election. Both campaigns and many political pundits say Ohio could decide the election.  How secure are its voting machines?