Dell application support does not find my service tag or express service code?

When I enter the service tag or express service code manually again dell does not find it.  Need drivers for several unknown items in device manager. I need help finding the right drivers after a system crash and re-installing Windows XP.  This is an XPS Dimension Gen3. I have tried typing in my service tag or express service code manually.  Dell does not find it in its database. I've tried the approach of asking Dell to find my service tag or express service code for me.  This also fails: dellsystemdetect.application. It produces a lengthy wait followed by a message that it didn't work, and I should try again later.  I need drivers for several unknown items in device manager, and I also need to find out why I cannot install Windows 8 from the CD. Any help you can offer will be gratefully received.
Thanks,

Bonnie