Using textures in-game

Got a quick question. Is there a particular reason that my computer slows down so much when I add even one 512x512 texture into the game? It’s for a skybox, just so you know.

Textures take a lot of FPS in games. But some major slowdown just because of 512x512 skybox shouldn’t occur. What PC do you have?

It is a 2002 computer, with an AMD Athlon 1.33 GHz processor, and 256 MB of RAM.
Oh yeah, and my graphics card is a NVIDIA GeForce MX 440 card, a really cheap card with no shader support and no extra RAM.

There’s your problem, your graphics card and RAM. Although it’s true that after 1 Gig of ram more doesn’t cause major speedup (if you have 1 gig, and the next guy has 32 gigs, it makes no big difference in games) but graphics cards mean everything. Go buy yourself a nVidia GT or PNY

How much will I be looking at in terms of cost? I have an unfortunately limited budget.