I had to look high and low for these so I’ll put them here for next time.
http://support.dell.com/support/downloads/driverslist.aspx?os=WW1&osl=EN&catid=-1&impid=-1&servicetag=&SystemID=LAT_D531&hidos=WLH&hidlang=en
Update (found a forum post with driver file names):
Chipset:
Ricoh – Driver
Applies to:
R5C833
(R141246.exe – for SD/MMC card reader)
Communication:
Conexant – Application
Applies to:
D330,HDA,MDC,v.92,modem
(R148605.exe – Digital line detection – warns you if you connect to a digital switchboard. Useful if you travel but not vital for home use. For driver see below)
Mouse & Keyboards:
Dell – Driver
Applies to:
Touchpad / Pointing Stick
(R155586.exe)
Network:
Broadcom – Driver
Applies to:
440x 10/100 Integrated Controller
(R149798.exe)
Dell – Driver
Applies to:
Wireless 1395 WLAN MiniCard
Wireless 1505 Draft 802.11n WLAN Mini-Card
Wireless 1490 Dual-Band WLAN MiniCard
Wireless 1390 WLAN MiniCard
(R174291.exe)
You can find the remaining drivers in the download list for the Lattitude D531:
Audio:
SIGMATEL – Driver
Applies to:
STAC 92XX C-Major HD Audio
(R171789.exe)
Chipset:
AMD – Driver
Applies to:
Processor Driver
(R135384.exe – Support for AMD PowerNow! and Cool’n’Quiet)
ATI – Driver
Applies to:
SMBus / Chipset Driver
(R134875.exe)
Communication:
Conexant – Driver
Applies to:
D330,HDA,MDC,v.92,modem
(R147115.exe – This is the actual driver for the modem)
Video:
AMD – Driver
Applies to:
Radeon Xpress 1270
(R163694.exe – This complained that .Net was not installed when I first tried so I suggest installing everything else first and running Windows Update to get all the .Net 1.1, 2.0 and 3.0 updates before running this)