not enough space seems to exist in hard disk, cannot launch synaptic

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We appreciate the difficulties you are facing, but it would make more sense to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs. For help on reporting bugs, see https://help.ubuntu.com/community/ReportingBugs#When%20not%20to%20file%20a%20bug.

sudo apt-get autoremove
sudo apt-get clean
sudo apt-get autoclean

Or you can simply resize your Ubuntu partition with live CD or with gparted live CD witch you can download from
http://gparted.sourceforge.net/

 zvacet
thank you very much for your help
would it be safe to follow your instructions , as I'm a new linux user and
ubuntu installation shares disk with winXP files?So I'm not having an
exact icon of the partitioning of the disk.

The problem seems to be solved with a repartitioning of the disk with
livecd.I think, probably the parallel with winXP intallation procedure
could notify new users of the amount of space needed.At least for the
basics included in Ubuntu installation.
Thank you very much for your great support

this solved my problem