A general listing of Samsung Printers supported in WinXP x64.
The following printers have a driver for x64 (as of 12 Jan 2006) on Windows Update:

Samsung CLP-500 Series
Samsung CLP-510 Series
Samsung CLP-550 Series
Samsung MFP 560 Series
Samsung MFP 750 Series
Samsung ML-1450 Series PS
Samsung ML-1510_700 Series
Samsung ML-1520 Series
Samsung ML-1610 Series
Samsung ML-1650 Series PS
Samsung ML-1710 Series
Samsung ML-1740 Series
Samsung ML-1750 Series
Samsung ML-1750 Series PCL 6
Samsung ML-2010 Series
Samsung ML-2150 Series
Samsung ML-2150 Series PCL 6
Samsung ML-2150 Series PS
Samsung ML-2250 Series
Samsung ML-2250 Series PCL 6
Samsung ML-2250 Series PS
Samsung ML-2250M PCL 6
Samsung ML-2250M PS
Samsung ML-2550 Series
Samsung ML-2550 Series PCL 6
Samsung ML-2550 Series PS
Samsung ML-2550S Series
Samsung ML-2550S Series PCL 6
Samsung ML-2550S Series PS
Samsung ML-2560 Series PCL 6
Samsung ML-2560 Series PS
Samsung ML-3550N PCL 6
Samsung ML-3550N PS
Samsung ML-3560 Series
Samsung ML-3560 Series PCL 6
Samsung ML-6060 Series PS
Samsung ML-7300 PS
Samsung ML-7300 Series PCL 6
Samsung SCX-4100 Series
Samsung SCX-4214F
Samsung SCX-4x16 Series
Samsung SCX-4x21 Series

To install a driver for those printers, gdo this:
Control Panel -> Printers and Faxes
Right Click -> Add Printer
Next -> Local Printer attached to this computer
Activate "Automatically detect and install my Plug an Play Printer" and click Next.
Your printer should get installed (may take a while)

To manually install a driver (if autodetection fails):
Don't activate the option "Automatically detect and install my Plug an Play Printer" and click Next.
Choose the Port your Printer is connected to and click Next.
Click Windows Update.
Choose Manufacturer and Model and click Next.
Finish the wizard.

Thanks