Enter the Bios and change the Drive Controller setting to  RAID Autodetect/ATA  save changes on exit, Xp will install now.

 

http://support.dell.com/support/edocs/systems/dim8400/SM/syssetup.htm#wp1052327

how to enter your bios (system setup)

 

When you are in the bios your navigation keys will be listed at the bottom of the screen.

" Re-installs require that all PCI-expansion Cards be removed...also remove your Memory Modules just leaving a single in SLOT-0(closest to the Processor).."

 

Not necessary on the 8400. Not true. I have never removed an expansion card or Memory on a Dell to re-install an OS, unless the card or memory module was defective.

 

Please provide documentation / Link for this statement.

 

Lets try to help the OP, not confuse them with erroneous statements.

 

 

Re-installs require that all PCI-expansion Cards be removed...also remove your Memory Modules just leaving a single in SLOT-0(closest to the Processor)..

F-2 System Set-Up should be configured to CD-ROM..and the very end of your FLAT Cable is the BOOT-Drive....

I most often these days use a Paper Clip to POP-open the BOOT Device...place the OS CD inside...push closed...and just BOOT from a DEAD-start....Tapping F-12....//[end]