There is a change in FSB frequency from 400 to 533 during the production of Pentiums 4 cpus. My info says 1.6 1.8 2.0 and 2.6 used 400 Mhz and 2.4 2.8 used 533 Mhz. I can't find any information from Dell on what the Bios updates might fix or if your motherboard can even work at 533 Mhz. I did find this info from a memory supplier that listed the Dell model number with 533 FSB:
A few of the 8200s have a motherboard which will support a 533 front bus speed, these can use the PC1066 RDRAM. When in doubt, give us a call at 1-800-566-3727 to help you determine exactly what you need.