I'm afraid that my laptop will break if I install this link http://cdimage.ubuntu.com/...p-i386.iso because I have a Windows Vista laptop.
This is an ISO file. So a system image, or an identical image of a DVD, CD or similar. Should it be a system image, nothing should happen, as long as you do not boot your PC over the file. Why do you want to download the file?
Because my laptop is too old.
Linux makes your laptop faster, but obviously you do not have that much idea, either do it with someone you know or buy your new PC / laptop. Only by the download laptop will definitely not faster. You would almost take instead of windows Linux as the operating system.
Once you've downloaded the file, it's simply on a hard drive. It is not executable. To use them, you have to use them, e.g. Burn to a DVD (ie ISO, not as a file!) Or make it bootable with the appropriate software on a USB stick - and then restart the laptop with inserted DVD or Inserted stick.
Then you may still have to select at startup that you want to start from this external medium. And then you have yet to select that you want to install the operating system of the medium on the computer.
And only then will it be "dangerous" for Vista, because then you can override it. If you do not want that, you can also install Lubuntu next to Vista (read very carefully what the system wants from you!) Or test it "live" without installation.
The latter I would definitely recommend, because Lubuntu is a little different than Vista. Also, you can see if the new system is compatible with your laptop.
The laptop certainly will not break.
