When I download some files ,it begins but at the end fails showing one message(operazione non riuscita) thus download ended and failed. I use hp pavilion windows vista ,Google crome.

The only thing I can think of is the following:
1. Uninstall and install chrome
2. Update internet explorer
3. Reset internet explorer and delete all plugins for chrome.
4. Anti Viruse or Firewall Application can also cause this. Uninstall yours and restart.

Also try creating a new user(administrator). Log in with that account and try again.
Also try the system file checker. Start run (Windows key plus R key). In the Run box type:
Sfc /SCANNOW

Hope this helps
Grant

I disagree with these answers. You should first rule out the browser by running another and see if the error persists. If the other browser successfully completes the download, then try removing addons and plugins as suggested. If your other browser does the same thing, it could be your router, or some other networking issue. I would then rule out one or the other by plugging into your router directly. If it's an ip problem, or a wireless signal problem, your downloads will start working. If it's a wireless problem, then log into your router and "release" your ip address. The router will then assign you another. If the problem persists, try a different wifi channel or relocating or rebooting the router.