There are no official windows 7 drivers for this model. After installing windows 7, you will notice most of the drivers installed except the AUDIO and GRAPHIC (nvidia 8400). If your model use Intel 965 graphic windows normally installed the WDDM drivers for it.
AUDIO DRIVERS.
Download the original vista drivers:
http://ftp.us.dell.com/audio/R171786.exe
Step to Install:
1. Right click on the R171786
2. Select Propertise.
3. Select compatibility tab.
4. Tick on the "run this program in compatibility mode for"
-Select windows Vista or vista sp1 or vista sp2 (select only one)
5. After that click apply and ok
6. Right click again and select run as admin to install.
7. reboot after installation finish.
GRAPHIC DRIVERS:
DELL inspiron 1420 comes with either INTEL 965 Graphic or Nvidia 8400. Model with Intel 965 normally automatically installed along windows 7 installation. If it did not you can get the latest win 7 driver here:
Intel 965 Drivers for 32-bit and 64-bit.
http://downloadcenter.intel.com/SearchResult.aspx?lang=eng&ProductFamily=Graphics&ProductLine=Laptop+graphics+drivers&ProductProduct=Mobile+Intel%C2%AE+965+Express+Chipset+Family
Click on the link and you will be redirected to the intel site, there look for Intel graphic media accelerator for win 7.
NVIDIA GRAPHIC DRIVERS:
Download x86 (32-bit)
Downloadx64 (64-bit)
CARD READER
From my experience, most laptop wont install card reader by default, so you need to install the card reader using the same method to install the audio drivers:
Download the drivers here:
Download link
If you have other drivers missing do let me know in the comment section below.