Can i somehow continue with a rendering?? I have maded an animation but it’s in 670 frames!! And i got 2 brothers and 1 sister that want to use the computer as well! 
Or i can render lets say 1-100 frames then save the movie and next time render 100-200 and then put them togheter with some program. Do you think this can work? And if do you now any program?
sure. Blender can do that. Try to play around a bit with the sequence editor.
You can set start frame and end frame in the rendering window. If you create single images and not an AVI you’ll get all frames one by one.
Then in the sequence editor of Blender itself ypu can load all frames and make the AVI!
Stefano
(P.S. you can launch the rendering from the command line. Try blender -h for help. This is faster because it does not use graphics 
And if you have a serious OS (NT, WIN2000, LINUX) you can renice down the process so that you almost don’t realize it is rendering while you do other things)
You can also use external programs like VirtualDub to append the video-snippets. I find this faster than working with blenders sequence editor.
If you have enough disk space, I’d highly recommend rendering out as a TARGA sequence. Then use Blender’s Sequence Editor to put them all together into an AVI when you’re done. Rendering out individual frames will also prevent you from loosing your entire rendered animation if the power goes out or something.