Can't start up an already installed Windows 7

Computer info:
The laptop has an Intel Core i3 processor, 4 GiB of RAM and about 300 GiB of HD storage space. No physical video card.
System info:
I'm using Ubuntu 10.10 64-bit. I have VirtualBox OSE 3.2.8 and I have installed Windows 7 64-bit with VB OSE placing the OS in a file of fixed size 26+ GiB. The system is already installed (with no problems during installation itself) and all configurations are set up [apparently] properly, but when I click the "Start" button in VirtualBox OSE the following error message appears out of the blue: (follow the link to see a snapshot of the error message)

http://3.bp.blogspot.com/_MDFOchUX_Rk/TPL88iBMz0I/AAAAAAAAAOo/pFpVLeqEPCk/s1600/VirtualBox%2BOSE%2Berror.png

I need YOUR help. As a 5-month Ubuntu user I'm clueless about this. I wiped Windows out of my laptop a couple of months ago, but now I need it to run Windows-oriented software, and I'm not planning to install Windows back on my laptop. The software I need to run DOES NOT WORK WITH WINE. VirtualBox seems to be the only way, but now I'm stuck with this. Thanks in advance for your help.