Help with stop:0x00000050

I'm having an issue installing XP SP2 from a boot disc on a machine that already has Vista Home Premium. Whenever I throw the disc in and start it running, it's able to load all the drivers and start Windows, but when it gets to the partition manager, all it has to list is "Unknown Device" and so I tried pressing "c" to create a partition in the free space, but nothing happened. So I just hit enter to begin installing it and I get the error to do with setupdd.sys PAGE_FAULT_IN_NONPAGED_AREA. STOP:0x00000050 (0XE199D198 0X00000000 0XF75C99A8 0X00000002.

Thanks in advance to anyone to tries to help.

Please read both these links on creating a Dual boot system:
http://windowshelp.microsoft.com/Windows/en-US/Help/00d076cd-6e10-42d6-a4ef-de55d9f4c0201033.mspx
http://apcmag.com/how_to_dual_boot_vista_and_xp_with_vista_installed_first__the_stepbystep_guide.htm

Thanks. That helped nicely.