I installed ubuntu on both of my laptop and desktop and logged in ubuntu one using the same account.Now on my laptop I can see the sync folder of my desktop although I have already uninstalled ubuntu from my desktop.How can I delete the left folder from my ubuntu account?
When you synchronize two computers, you get an identical copy on each. You can delete it, but if you do, then it will also be deleted from all your other computers and from the web. That's what synching means.
Edit: If you want the folder to be deleted from all your computers, delete it on a synced computer, just as you would delete any other file. The deletion will then be synchronized to Ubuntu One and to all your computers.