Shawn,
I spoke incorrectly above because I thought you said you had been found NOT guilty.
Expungements are only for the innocent, falsely accused, and others who were prosecuted for or accused of but not convicted of a crime. There is a great PDF primer Virginia puts out:
http://lsnv.org/Information_Expungement.pdf
At this point, you would need to seek a pardon.
pardon attorneys are very expensive, I hope you have access to a lot of money and little expectation of receiving one. even in pardons, there is a type that does not expunge the record, and merely forgives you for the crime. this one is the only one I could see you obtaining, and it still seems a bit daunting. a conditional pardon is for those in prison right now, and an absolute pardon is like the Gutenberg bible. Very rare.
I recommend you not sweat it. If you are willing to show the courts docs to future employers, and clearly explain your side of things, most jobs that don't require clearance probably would let it go if all other factors are good. Probably any job involving driving would be out, too, but big loss. All those jobs suck anyway.