Ensure you reference your service manual before carrying out upgrades:
The most recommended upgrade for this system is a Solid State Drive, here is my affiliate link to Crucial here. If purchasing a SSD or Memory Upgrade please use these links as I will get a tiny bit of commission which will help fund my guides.
SSD Drive Upgrade
This system has an unpopular ZIF connector opposed to a SATA connector… this is problematic because it means that most SSDs will not fit in this model and mainstream vendors such as Crucial do not list any SSD compatible upgrades. It is possible to get a mSATA to ZIF connector as outlined here. Crucial are not really selling mSATA SSDs these days and only older models for an obscene price as sold on Anazon. So you are best to use either a Kingston or a Samsung mSATA SSD.
This upgrade has been tested in the Latitude D430 but not the Latitude D420 but they use the same type of Drive.
This system supports 2.5 GB of RAM (1×2 GB Modules and 0.5 GB soldered to the motherboard). This can also be purchased using the affiliate link above.
It is recommended to install Windows 10 on this system see Windows OEM FAQs and Downloads. The Windows Vista OEM or Windows XP Product Key won't be compatible with Windows 10 Installation Media however you can run Windows 10 Unlicensed. Windows 10 will have most of the system drivers required inbuilt however you can install the Windows 7 Drivers if you have any unknown Devices in the Device Manager.
Note 64 Bit compatibility depends on the processor installed and as the system maxes out at 2.5 GB RAM it is not recommended to install 64 Bit over 32 Bit on this model.
Drivers and Downloads for Windows 7
System Utilities (Windows 7 Only)
Chipset (Windows 7)
Video (Windows 7 Only)
Communications (Windows 7 Only)
Not all systems have a modem. If the Driver fails to install, there is no need to try and install the rest in this category.
Dell Wireless Cards
Audio (Windows 7 Only)
Check the Architecture of the link and then select download.