Deltadom, I do not personally agree with infant baptism, but have many friends who do. It is important to remember that many who do practice it do not believe that baptism makes anyone "born again" or "Christian".
Reformed churches believe that baptism is a [b]sign[/b] of the New Covenant. The sign simply points to the real thing: that one can only enter the new Covenant through repentant faith. They baptize their children because they believe God wants to give children of believers an evangelical witness, beginning when they are young. Reformed Christians teach their children that God wanted them baptised to remind them about what they need: to die with Christ and be raised through faith in Him.
They see infant baptism as being very similar to infant circumcision in the Old Testament. Circumcision was given to Abraham as a sign of his faith (Romans 5). Both of Abraham's children were circumcised before they had shown faith, and one turned out not to have faith. Esau and Jacob were also circumcised as infants, but only one ever had true faith. (Romans 9)
Just like circumcision told Jewish children that they needed their sinful hearts to be "cut off", so Reformed Christians believe God gives baptism as a special blessing to children of believers by showing them from a young age that God requires them to die and be raised with Christ through faith.
Hope that helps.
