I am not able to install JMS Multisite into my joomla 1.7 i get this error: There was an error uploading this file to the server.

Please help
I have download the package com_multisites_V1.2.68.zip

As you can read several times in the forum, this is the symptom that your server has probably a limitation to upload huge pacakge.

JMS is almost 4MB and your server must accept to upload such size that does not seems the case.
See the tutorial video 3 that gives an alternative solution to install from a directory
www.jms2win.com/en/tutorial#jms12x-3
tutorial.jms2win.com/joomla/multisite-12...stall-from-directory
In case of Joomla 1.6 or 1.7, you have to use the subdirectory _j16 to get the manifest file for the joomla 1.6 or 1.7