You can't. You can upload it to a server and provide a link to it, though.

Also, you can use the code and source tags to put code in your posts (more information in this section of the FAQ).

That particular feature isn't offered by the GDNet forum software (and personally I don't think it should be).

As mentioned, if you want to show some source code, you can use either code (shorter samples) or source (longer samples - also includes syntax highlighting) tags as described in this section of the main forum FAQ.

You can include images in your posts using regular html, but you'll need to host them elsewhere. Again it's described in the FAQ, and if you're in need of hosting to do this you could use the free ImageShack service.

Any other files you'll just have to host somewhere and link to. If you'd like to get a small amount of hosting you could use for this (I believe we currently provide 50MB) and support the site a bit you could invest in a GDNet+ subscription, which includes a few other benefits such as the ability to have a display picture and a journal.

Hope that answers your question. [smile]