VirtualBox-4.3.16-95972-Win is out, & this one seems to work for more people, myself included, than their last release. The devs "hardened" V/Box, & their forum thread for problems with this version seems to me to hint that that hardening caused problems with security software. Regardless I'd suggest using Time Freeze or similar until you verify it runs.
If you're new to VMs [or VirtualBox], download VirtualBox-4.3.16-95972-Win.exe & Oracle_VM_VirtualBox_Extension_Pack-4.3.16-95972.vbox-extpack from the virtualbox.org site. Run the 1st .exe file to install, then run it as admin. Now go to the File -> Preferences menu, click Extensions, & then click the top icon on the right [with the yellow triangle] to install the extension pack you downloaded.
If you're in win7 or 8/8.1, I suggest creating an expanding VHD virtual drive file in Windows, rather than using the V/Box .vdi format -- that way you can mount & access the virtual drive in Windows, just like any other drive, which can be handy on occasion, e.g. you can mount it, back it up with something like Paragon & restore to another drive, virtual or real, or copy the partition etc. When we built a PC for my oldest son I cloned the partition from a win7 VM to his hard drive, connected it to the new PC, & 5 minutes later, having run Paragon's hardware migration from a CD, the PC was running a fully up-to-date copy of win7 HP 64.
Anyway, back to V/Box... Go to the Machine -> New menu, and really just follow the prompts, pointing it to the VHD you created, or letting it create a new .vdi. The V/Box Manager window shows all your VMs on the left -- if you select one & go to the Settings menu, that's where you can change things, in this case adding your Windows installation disc or ISO to the VM [using the Storage menu], & setting it 1st in the boot order [System menu]. When you start your new VM you'll see the same things as when you install Windows on a real PC or laptop.
Once Windows is installed go back to the settings, replacing your Windows install disc or ISO with the VBoxGuestAdditions.iso located in the V/Box program folder [C:\Program Files\Oracle VM VirtualBox]. There may be a task bar pop-up or a menu item to install the additions, but I've found they often don't work, so I just navigate to the DVD drive in the VM using Windows Explorer, & run the additions setup file from there. Note that the D3D drivers are installed in Safe Mode -- use msconfig to boot into safe mode, add the drivers, then run msconfig again to turn Safe Mode off.
Once you have the additions installed things work a Lot better, so now it's time to head to Microsoft Update to get your VM copy of Windows current. Everything pretty much works the same as Windows on a real PC, so you can add pretty much whatever software you like. When your VM's running there's a menu at the top of the Window -- go to settings & you can add a folder or folders to share between regular Windows & your VM -- that's how you get files in/out of it. I have a network capable printer -- I installed the printer software in a VM the same as I install it on any other networked PC, & it works fine [in the VM I use it mainly for printing coupons].
What I do, & this is just me, is I copy the .vdi or .vhd file that's the virtual hard drive for a VM to another location [in my case on a 2nd drive] after clearing out the temp files, ie cache & such. Install something I don't like, or just test out a few apps, & I can restore the VM by copy/pasting that copy of the .vdi or .vhd on top of the one the V/box software uses. Those virtual disks don't back up very well in my experience, so I'll also delete them from my C: partition before I back it up, then copy/paste them back.