Dell no longer provide support for this model especially for windows 7. You may have problem with driver especially audio drivers for windows 7. So i make this post for Dell vostro 1400 windows 7 upgrade guide.
LAN/Ethernet Driver
Broadcom 57XX Gigabit Integrated Controller,
v.12.2a.4.1, A00 Download
Audio Driver:
SIGMATEL STAC 92XX C-Major HD Audio,
v.6.10.0.5614, A03 Download
Chipset Driver:
Intel Mobile Chipset Driver
Download
Card Reader Driver
Ricoh R5C832, R5C843, R5C833,
v.1.0.1, A00 Download
Modem Driver
Conexant D330,HDA,MDC,v.92,modem,
v.DLD1.21, A01Download
Webcam Driver
Creative Labs Laptop Integrated Webcam,
v.R2RC1, A04 Download
TB Driver
Intel Turbo Memory,
v.1.0.0.1082, A00Download
Storage Driver
Intel Matrix Storage Manager - Notebooks,
v.7.0.0.1020, A02Download
Graphic Driver - Nvidia
nVidia GeForce 8400M, GeForce 8600M, GeForce 8400M GS
v.175.97 xp WHQL, A08 (vista - v.179.47, A13)
Windows XP : Download
Windows Vista : Download
Windows 7 : Download
Graphic Driver - Intel
Intel GM965 Express Chipset Family,
v.6.14.10.4831, A01(xp) (vista-v.7.14.10.1272, A02)
Windows XP : Download
Windows Vista : Download
Download (win 7 32-bit)
Download(win 7 64-bit)
Touchpad Driver
Dell Touchpad / Pointing Stick, v.10.1.2, A01
Windows XP/Vista Download
Download (win 732-bit)
Download (win 7 64-bit)
LAN/Ethernet Driver
Broadcom 57XX Gigabit Integrated Controller,
v.12.2a.4.1, A00 Download
Audio Driver:
SIGMATEL STAC 92XX C-Major HD Audio,
v.6.10.0.5614, A03 Download
Chipset Driver:
Intel Mobile Chipset Driver
Download
Card Reader Driver
Ricoh R5C832, R5C843, R5C833,
v.1.0.1, A00 Download
Modem Driver
Conexant D330,HDA,MDC,v.92,modem,
v.DLD1.21, A01Download
Webcam Driver
Creative Labs Laptop Integrated Webcam,
v.R2RC1, A04 Download
TB Driver
Intel Turbo Memory,
v.1.0.0.1082, A00Download
Storage Driver
Intel Matrix Storage Manager - Notebooks,
v.7.0.0.1020, A02Download
Graphic Driver - Nvidia
nVidia GeForce 8400M, GeForce 8600M, GeForce 8400M GS
v.175.97 xp WHQL, A08 (vista - v.179.47, A13)
Windows XP : Download
Windows Vista : Download
Windows 7 : Download
Graphic Driver - Intel
Intel GM965 Express Chipset Family,
v.6.14.10.4831, A01(xp) (vista-v.7.14.10.1272, A02)
Windows XP : Download
Windows Vista : Download
Download (win 7 32-bit)
Download(win 7 64-bit)
Touchpad Driver
Dell Touchpad / Pointing Stick, v.10.1.2, A01
Windows XP/Vista Download
Download (win 732-bit)
Download (win 7 64-bit)