Acceptable file types.

Image files.
.png or .jpg (or .jpeg) or .gif work correctly.
.bmp will attach but not display (they show as a filename only).
.tga and .tif (or .tiff) will not attach.

Other files.
All other files such as .max, .3ds, .fbx etc must be zipped using WinZip (or equivalent).
Other compressed file types will not attach. This includes (but is not limited to) .rar .7z .arc.

Note. Using an alternative file compressor and renaming the files to .zip is not acceptable. It causes users no end of confusion.

Important. Files beginning with “_” (underscore) will NOT attach. This affects avi’s created with “Make Preview”.

Attaching the files

Click the “Browse” button, browse to the file and OK it.
If you need a second file, click the “Add Attachment” button and repeat the above.
Submit the post.

DO NOT, under any circumstances, click “Preview” if you already have files attached - they will be lost.
The “Add Attachment” button does NOT submit the file - it merely opens up another entry field for you to add another file.

Note. If you click Add Attachment but do NOT actually add another file, all existing attachments will fail when the post is submitted.

There is (or is supposed to be) a 3.5MB size limit (sum of attachment sizes per post).

Max 4.2 through 2010, XP-Pro 64 SP2.
NVidia 8800GTX-768 (Driver 185.85).
Core 2 Quad Q6600 2.4GHz, 4Gb Ram, 4Gb Swap, DX9.0c.