I reinstalled Windows XP and I am missing the driver for "Modem on High Definition Audio Bus". What is that?

You could disable it in device manager. If you uninstall it might pester you again later.

Though having a modem can be handy. I am surprised about twice a year when the need arises, either for faxing or when broadband is unavailable.

It might be the driver labeled “Conexant D330,HDA,MDC,v.92,modem” on this page:
Drivers & Downloads for Latitude D530

I am guessing HDA = High Definition Audio

Also I would recommend installing the Intel chipset driver. On recent fresh installs, I found the chipset driver was not installed from the disk or Windows update, and getting it cured some performance woes.

@jaytkay Thanks for the help. That was the right driver. I also threw the Intel Chipset on there too.