This is the newest official version of windows. Windows 8 is being developed but it isn't official yet. You can download a preview of it to install to your computer if you want.
Windows 7
WHAT? OS stands for operating systym. Windows 7 is the newest one
Mac OS X 10.5 (Leopard)
their is a compatibility mode, try it or else use dual OS
4.2.2 (Jelly Bean)
Yes. All linux based OS's can be installed at side or over W7.
Linux comes closest to mind.
It's a Mac Os X Lion.
This question is impossible to answer, because in the time between me answering the question and anyone reading it, a new application or two will have come out. If you mean the newest operating system, or software base, Chrome OS(http://en.wikipedia.org/wiki/Google_Chrome_OS) is the newest major one to come out.
bcuz i sed
August 2012. The OS is called Mountain Lion.
The newest and final form of Windows XP is Windows XP Service Pack 3. As of 2013, the OS will no longer be updated or upgraded.