Upgrade Exchange 5.5 to Exchange 2003

Hi,
I have NT 4.0 PDC and Windows 2k member server with Exchange 5.5+SP3. I already upgrade NT 4.0 to Windows 2003 with ADC all users can logon to new ADC (windows 2003 server). My question is how to I upgrade old windows 2k member server with exchange 5.5+sp3 to Exchange 2003? Please advice.