Installing Guest Additions
With Windows XP updated and booted, it's time to install some VirtualBox optimizations. Unbind the mouse from the VM by pressing the right Ctrl key. Click on Devices in the menubar of XP's VM window, then click Install Guest Additions.
The Sun VirtualBox Guest Additions setup screen should open. Rebind the mouse to the VM by left-clicking anywhere on the Windows desktop. Click Next, I Agree, and then Next again. Check the box next to Direct3D Support (Experimental) if you plan on utilizing DirectX 3D graphics. Click Install to begin copying the Guest Additions files to your VM. When Guest Additions is done installing, click Finish to reboot.
After Windows has rebooted and you're back to a workable desktop, a VirtualBox icon will be in the notification area of the taskbar. If you had previously resized the desktop's resolution, it may have reverted back. Also notice that your mouse is now able to move between the VM and host OS without clicking or using the Ctrl key. This is called Mouse Integration and is part of Guest Additions. It can be turned on and off from Machine in the menubar, or by pressing right-Ctrl+I.
Remember the shared folder we designated when we tweaked XP's VM settings? You're going to need it now. Navigate to the shared folder in your Linux file manager (mine was the Public folder in my Home directory, /home/adam/Public). This is where you'll put files from Linux (the host OS) that you want to share with Windows XP (the guest OS). This is also where you go to receive files from XP to Linux.
To make files from Windows XP available to the Linux host, or to receive files from Linux in XP, you need to first boot up the XP VM. In this step, the sequence must be followed to the letter. This is very easy to get wrong, and a misstep will result in you starting over.
Follow the mouse pointer in the screenshot below for easy reference. From the Start Menu, open My Computer, then click My Network Places in the Other Places sidebar. Next, click View workgroup computers in the Network Tasks sidebar. Now, click on Microsoft Windows Network in the Other Places sidebar. Click on Entire Network again, in the Other Places sidebar. Now, there should be an entry for VirtualBox Shared Folders in the window. Double-click it.
Your shared folder should be there, listed as \\VBOXSVR\"folder name.” For example, mine is \\VBOXSVR\Public. Since it's such a hassle to go through the XP file manager's sidebar to get here, it's a good idea to put the shared folder in your Favorites. Just click Favorites/Add to Favorites when you're in VirtualBox Shared Folders. From now on, you can get to the VirtualBox Shared Folders directory from Favorites in Windows Explorer.
Now you'll be able to easily transfer files between the Linux host OS and the XP guest OS.