The processor power has really nothing to do Virtualbox working good or not.
If you just want to run Windows by itself your setup should be fine.
You can tell Virtualbox how much memory to allocate from the system to
the Virtual session.
If you want to use other programs while Vbox is running you will have to
experiment.
I have found on my system with Thunderbird, Firefox and Vbox open with a
Win2K session my system is stable and Windows actually runs faster then
if it was installed by itself on the computer.
This all with Ubuntu 8.04 and I won't tell you my system specs but I do
have 2GB of memory. Most times memory is all you need to install to help
your system run more stable and sometimes faster.

73's is used with amateur radio operators to mean "My compliments, or
Best Regards"
http://www.signalharbor.com/73.html