CPU:  the first-generation Core i only.  You may be able to use a dual core i7-7xx CPU.

GPU: no way to upgrade

Express card depends on what you want to connect -- no, it cannot be used to upgrade the GPU, but it could be used for a USB 3 card, etc.

Welcome to the Dell Community @crazyst0rm 

Since your CPU is the i5-520m you have the Socket G1, based on the Arrandale core.

These would be the CPU's you can use.

https://www.cpu-upgrade.com/CPUs/Intel/Core_i5_Mobile/i5-520M_(PGA988).html

Best regards,

U2

Upgrades

Check to see what motherboard you have it’s the only way you will know to what you can upgrade to. There are 2 one has Intel integrated gpu and the other has Nvidia. If you’re lucky enough to have the Nvidia nvs 3100m (LA-5573P) you can actually upgrade to a quad core 1st gen i7 CPU’s and there’s a few to choose from- 720qm, 740qm, 820qm, 840qm and the two extreme editions 920xm and 940xm. This M.B. also allows for up to 16gb ddr3 ram @1333mhz to run in dual channel mode. If you have the Intel board (LA-5571P) then you’re pretty limited as far as upgrades and are stuck with 1st gen dual core CPU’s @ 8gb ram. Either of these are capable of running sata ssd’s which is a pretty good start for sure!! 

Confirm all that @Slayer_81 wrote, it's same for the brother E6410 with these CPU's, speeding up at 1333MHz and with the latest A17 BIOS like RAM perfectly for 16 GB, 2x8GB in Dual Chan

https://www.dell.com/community/en/conversations/latitude/dell-latitude-e6410-16gb-ram-on-latest-bios-in-2023/652c1aedea4fe00b019c8bf4​

:

:
|[KB's on RpZ]|