I saw your question going unanswered so I thought I might take a crack at it.
So here goes...
The HP Laser Jet P1005 (which I think is what you meant by HP1005) is not compilable with Win7 and has been discontinued so HP no longer is updating the driver.
However - you may be able to install the Vista driver and run it in compatibility mode. That may work for you, if you haven't already tried that. I have had pretty good luck with their compatibility mode in the past. Though it's not a sure thing. Using that route may require trying different drivers until you find the right one. That's always given me headaches.
May I suggest that you try Windows XP Mode/Windows Virtual PC on your Windows 7 Ultimate computer. Microsoft has seen these problems with many companies and users migrating to Win7 and trying to use their older software/hardware.
Windows XP mode and Windows Virtual PC for Windows 7 Ultimate is offered as a free download on the Microsoft website and looks to me to be a better long term solution to your problem. That is unless you have many things installed on your VB-ose that you can't afford to loose. I'm not sure if they support guest additions on WVPC. But they do offer USB support.
You can find them by following the link I have provided or go directly to Microsoft Virtual PC site yourself. http://www.microsoft.com/windows/virtual-pc/
Trying to talk you thru what you are suggesting is beyond my expertise at the present time. And may lead to other networking issues. I don't have Win 7 but I do use virtual box and have USB issues myself. I had troubles getting it to recognize my Cruiser drive.
You should be able to add it by going to your VM and selecting USB drive filters and add a filter from the attached device though you may have to add an empty filter and set that up yourself. That looks to be a pain also. I always use Microsoft Virtual PC for my Windows Guest on a Win host and VirtualBox on Linux. That's what drew me to your question. i did research it for you though and the aforementioned method is what I came up with.
I just found something on the virtualbox.org website on network printing. http://forums.virtualbox.org/viewtopic.php?t=1465
I know I haven't answered your question directly It would be too much typing and require a back and forth dialog to get it set up correctly without breaking your network and loosing your internet connection. But I feel it may solve your problem. Though if you are dead set on maintaining your Virtualbox system then try the VB forum link on network printing or look in the VirtualBox help contents file from the help menu. Personally I think I'd go with the Windows Virtual PC. myself, it would be a long term solution and is endorsed and supported my Microsoft to work on Win7 for your type of problem and should not have any issues like VB may in the future.
Hope that helps
Peace