Ok, so I'm a PC noob, and I'm 99% sure this is EVERYTHING to do with my PC. Anyway, I load in the mod with Optifine (I always use OF) and Forge. When I look at the locos tab, 4 of the locos are unrendered/invisible, and 3 are partially rendered. They have shapes, but no colors. Just plain white. The passenger cars are fine. When I click on the stock tab, the game crashes. Also, I keep getting this in chat:

OpenGL error 1285: (Out of memory)

Why is this happening?

Here are my specs (btw, this is a really old refurbished PC)
2 GB RAM
32-bit Windows 7 Professional
System manufacturer: Dell
System model: Precision WorkStation 390
System type: x86-based PC
Processor: Intel Core 2
RAM: 2 GB
Virtual memory: 4 GB

By the way, can I use a flash drive to get more RAM?

https://github.com/cam72cam/ImmersiveRailroading/tree/master/resourcepacks

You get the error because you are literally out of memory. Your graphics card doesn’t have enough vram to display all the models. You will need to blacklist some rolling stock to use this mod. Look in the LowResourcePack to see how stock is blacklisted (and won’t get loaded)

What's the LowResourcePack???