I want to use non-power-of-two textures. I found documents mentioning ARB_texture_non_power_of_two and GL_NV_texture_rectangle but none of them is defined in my gl. How do I use these extensions and what do I need/download to get them work?

If you don''t have drivers that support them, then there''s nothing you can do about it, except download newer drivers and hope it''s there, or buy a new graphics card.

You can simulate your it by using a part of a larger texture, and adjust the texture cooridnates. Check out glTexSubImage.

1st, I don''t think that it''s something about buying a new hardware. The problem is my SDK, not drivers nor graphic cards. I have a very old version of OpenGL SDK, and it''s simply not defined in the related header files.

2nd, I don''t want my image "corrupted" because I''m going to use this for graphics that are pixel art, and blur side-effect on resize is something I certainly don''t want to.

I asked how to use these extensions ( is it something that should be enabled, glEnable(...), or whatever), and where I can get the SDK that has these extensions defined.

Then check the extension registry. You will find some usefull headers there aswell.

Nvidia`s developer site is also a good place to start.
Use the search button to find OpenGL extensions, there will be a handful pdf document with all their supported extensions and an up-to date header file.

ATi also does that.