To restore the ability to control your speaker volume in Windows 8, you need to update the taskbar. In previous versions of Windows, this option was accessible through Sounds in the control panel, but it has since been altered. The taskbar contains your main icons and a set of grouped icons that appear in a collapsible group.
Right-click anywhere on the taskbar, and select the Properties option. This brings up the menu for the start menu and taskbar. With the first tab selected, click on the Customize button in the Notifications section. From here, there should be a list of various system programs. Scroll through the list until you find the volume control. Select the option to show it in the taskbar by checking the appropriate box, if it isn't checked already. Sometimes restarting can accidentally turn off the option.
You may also have to update the system drivers for audio programs. To do this, open Device Manager from the search menu. Scroll through the list of installed devices, right-click your speakers or audio card, and choose the Update Driver option. It is also possible to let Windows run a system update to catch any out-of-date drivers and install replacements.