Oracle has released a major version of VirtualBox 4.3 with several major updates and bugs fixed. As the best and free open source desktop virtualization software, now it supports latest Operating systems like Windows 8.1 and OS X 10.9 Mavericks. It’s highly recommended to upgrade (or install) uptodate version of VirtualBox extension pack which is 4.3.14 on your host computer. Here is the download link of VirtualBox 4.3.14 extension pack for Windows 8 & 7 and how to install it manually.
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VirtualBox extension pack gives USB 2.0 host controller support, RDP, PXE ROM with E1000 support. Its highly necessary to have better USB data transfer between host USB 2.0 devices and virtual machine.
By default when your host computer is connected to internet, VirtualBox program will pop up to upgrade the old existing extension pack. Installation is very easy with few clicks. In case you want to download and install virtualbox extension pack manually on other hosts which doesn’t have internet connection, you can directly download from below link. Just by double clicking the pack will update or install 4.3 extension pack.
Installation can be done in couple of ways, which already explained here how to install VirtualBox extension pack here.