Most apple fans thought that Microsoft copied their MacOS dashboard and widgets when first Vista screencaptures were on the internet and news, in fact Vista sidebar and gadgets are the equivalent of apple dashboard and widgets, some people says that Apple copied the sidebar from longhorn early releases (vista codename before it went retail) the truth is that copied or not Vista Sidebar really delivers what it was designed to do.
Microsoft included some gadgets with Vista, some of them were: a calendar, contact notebook, CPU Meter, RSS feed and notes. However gadgets uploaded by microsoft and thirdparties varies from a better version of the one I already mentioned to ebay bidders, IM contact lists, facebook, xbox live etc.
Most of them works flawlessly and if they dont we cant blame the sidebar itself, what is true is that the application can take a lot of system resources if is running more than one gadget.
On the other side, we are allowed to close each gadget individually to safe system resources, also if we have plenty of space on our desktop we can detach the gadgets from the sidebar and place it wherever we want, even make the sidebar transparent.
Windows sidebar will start by default with the operating system, but we can disable it as well just closing the icon on the taskbar and selected not to start automatically.
Although Vista Sidebar is only available on Windows Vista, a developer called SoKoOLz hacked it for Windows XP, however since it wasnt released by Microsoft its considered illegal and there are not direct downloads on sokoolz website.