virtualbox.org

I have done all- Total removed the previous version, it didn't work-- Installed the previous version and ran on top of the old Vbox still didn't work either.
Even if my processor is 64 bit, I am running 32 bit WinXP and I chose the 32 bit Virtual box 2.1.

By the way- I forgot to mention that my Athlon X2 3800 processor is 64 bit while my host operating system is 32 bits.

I am using Acer AMD Athlon X2 3800 with Windows XP and experiencing exactly same problem, I done the process many times. Looks like Vbox doesn't like this type of processor.
I had to roll back to 2.0.6. This version works fine.