Opera Software has put all its browser product download pages into one page at opera.com/download, means you can now able to download Opera for computer (Windows, Mac, and Linux), Mobile devices (Opera Mini, Opera for Touch and Android) and Windows XP/Vista, and a portable version (Opera USB) and archived versions from that page.
The new redesigned Opera download page also offers beta and developer versions of Opera for Windows, Mac, and Linux. The page provides both online an offline installation package to install the browser on your computer. Choose and proceed with one whichever you convenient downloading.
Opera has discontinued support for Windows XP and Vista with version 37, Opera 36 is last version to support XP, which is also available in this page for download. If you want to download Opera portable for Windows, the portable version is also available with name Opera USB.