you can get all your doubut at www.ubuntuforums.org
well for using programmes you dont actually have to dlownlaod it by searching. all you have to do is to find the name of the programme. you can give it a search on google. then for installing it, you would get a command. it is something like "sudo ....." . So all you got to do is click on application then accessories and select terminal and paste the command. press enter. you will be asked to type the password and the installition will start. the will ;et you know when it is complete. close it and use it. If you are adament abt downloading then just remember that .exe will not work. so almost all the formats are like .gz or .gt. i am not sure about all the extensions. any way you can also use the synaptic package manager or the add or remove package in the accessories. you will not have to actually download any file by yourself. the software will do it for you. anyway i too happened to discover that ubuntu is much better than XP have a great day.
