i make an particle effect but i dont know how to render it to videos.

help appreciated.

I don't think Houdini makes video files, only image sequences.

Try rendering your output to an image sequence then use 3rd party external software to convert the sequence into a playable video.

If you are just looking to preview, you can use the built in MPLAY.

Quicktime Pro will play a sequence and Fusion 8 is a free compositor if you need one.

Never, never, never, never render to video. 3DS Max allows you to do it, but it is such a terrible idea. If you crash halfway through the render, the whole file is corrupted. If you crash halfway through a JPEG or TIFF or EXR render, you start up again after you throw away the last file that was saved (almost always half done.) Go on your way without too much of a hiccup. Most render farms will restart after a crash and re-render last frame, and continue.

(I only suggest JPEG renders for quick previews. You should always render to 16 or 32 bit files. EXR files are preferred for compositing and color correction.)

render to frames
once the render is done you can use Mplay
load the frames into Mplay > Render > Mplay > Load Disk Files
now in Mplay > File > Export > there will be an option here to render a video.

however the options are not that great.
better would be to use a third party app to make your video.