Please check the troubleshooting guides before posting!

[plutomaniac]

something else might be wrong, attach HPL.log after the lagging occurs

[killmann95]

how do i do that? sorry if i seem like a total retard...

[plutomaniac]

check the sticky guides

[killmann95]

  hpl.log (Size: 3.77 KB / Downloads: 9)

[plutomaniac]

If you got the demo from Steam then do a file integrity check otherwise try a reinstallation

[killmann95]

still the same lagginess...

[plutomaniac]

Try disabling background applications/programs and lowering the graphics to the lowest possible. Your graphics card is not supported but works. That's all you can have.