installing win7 x64 in VirtualBox - error driver device missing

I ran into this problem today, you probably already solved your problem, but I'm just adding my experience as it may help somebody else.

(I used a physical install CD and not an ISO file)

1. Open your VM settings
2. Go to Storage
3. Select the CD-ROM drive
4. Check Passthrough
5. Boot the VM with the Windows

This solved it for me, so it might be worth a shot.

You can set a passthrough but this is also where you can point to an ISO file of your disc. I used an ISO because it makes the OS install much much faster and passthrough gets a lot of hiccups for long read times. Think of it as playing hot potato with 3 people instead of just 2.