Hello, my skybox textures are messed up!

Hello as you can see i have a problem with my textures may anyone help me?
http://s30.postimg.org/7m5527f4x/Gmod_bad_textures.png

when making a sky box use the tools/toolsskybox textures, then if you want to use a different skybox texture goto map – map properties and SkyBox texture name and enter it in their

It happens to every map i play on, space maps with stars and all that will just look white (and i dont make maps i just need help with my gmod)

go to SteamApps\common\GarrysMod\garrysmod\materials\ and look for a folder called skybox cut and paste tat skybox folder to your desktop then in steam verify Gmod game cache seehow te sky look after you have done that, if they are ok you can delete the skybox folder on the desktop, if there still the same have a look see if any addons are causeing the problem by disabling them

I cant find a folder named skybox!

they could be HDR skybox textures and you have hdr disabled check your options to enable it, also check your gfx cards can render hdr textures

How do i do that?
(windows 7)

you should see it in the video settings of the game

Still doesnt work!!