After I downloaded the SPH-A900 Contacts Copier (ver.1.2) and installed to my system, I browsed to the following directory and found some USB drivers:

C:\\Program Files\\SAMSUNG\\Samsung Contacts Copier\\USB Drivers

There are three directories under that folder, namely 1, 2, 3 and HSP. I have included ALL of them in the driver file. Feel free to try each of them (I suggest try 1 and 2 first as I found that they are most probably what you are looking for).

Here are some information of the SPH-A900 USB driver for each directory:

First Directory - 1

1. ss_mdmw.inf - Install the SAMSUNG Mobile USB Modem 1.0 Drivers (WDM) on Win9x
2. ss_mdmv.inf - Install the SAMSUNG Mobile USB Modem 1.0 Drivers (VCOMM
3. ss_mdm2.inf - Install the SAMSUNG Mobile USB Modem 1.0 Drivers (WDM) on Win2000/XP
4. ss_bus.inf - Install the SAMSUNG Mobile USB Device 1.0 drivers

Second Directory - 2

1. ssm_serv.inf - Install the SAMSUNG Mobile USB Port II 1.0 Drivers (VCOMM)
2. ssm_ser2.inf - Install the SAMSUNG Mobile USB Port II 1.0 Drivers (WDM) on Win2000/XP
3. ssm_mdmw.inf - Install the SAMSUNG Mobile USB Modem II 1.0 Drivers (WDM) on Win9x/Me
4. ssm_mdmv.inf - Install the SAMSUNG Mobile USB Modem II 1.0 Drivers (VCOMM)
5. ssm_mdm2.inf - Install the SAMSUNG Mobile USB Modem II 1.0 Drivers (WDM) on Win2000/XP
6. ssm_bus.inf - Install the SAMSUNG Mobile USB Device II 1.0 drivers
7. ssm_serw.inf - Install the SAMSUNG Mobile USB Port II 1.0 Drivers (WDM) on Win9x/Me

Third Directory - 3 (apparently for CDMA version of SPH-A900)

1. sscdvxd.inf - Install the SAMSUNG CDMA Modem (VCOMM)
2. sscdsdmw.inf - Install the SAMSUNG CDMA Modem Diagnostic Serial Port Drivers (WDM) on Win9x
3. sscdsdmv.inf - Install the SAMSUNG CDMA Modem Diagnostic Serial Port Drivers (VCOMM)
4. sscdsdm2.inf - Install the SAMSUNG CDMA Modem Diagnostic Serial Port Drivers (WDM) on Win2000
5. sscdbus.inf - Install the SAMSUNG USB Composite Device drivers
6. sscdwdm.inf - Install the SAMSUNG CDMA Modem (WDM) on Win9x
7. sscdw2k.inf - Install the SAMSUNG CDMA Modem (WDM) on Win2000

Alternatively, you can try the Free Driver Scanner.