According to service tag number
G34HG2J,
here is the Dell support and software site that's specific to that
Dell Latitude D420 laptop.
Here is the list of Vista 32-bit drivers for the devices in that laptop.
Here is the audio(sound) driver.
Here is the graphics(video) driver.
Here is the wireless network adapter driver.
Here is the wired network adapter driver.
You need to download and save all these drivers and then burn them off to a CD-R. If the install of Vista 32-bit doesn't install all the drivers, you can then install the ones your laptop needs from the CD-R.
Here is a pictorial guide on how to do a fresh install of Vista 32-bit.
You classify yourself as a beginner, so you're going to need help from a knowledgeable person to assist you.
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