I am a non-US citizen who left the US in 2007. On talking to my 401K administrator, I was told that I could cash out my 401K but 20% would be automatically deducted for tax purposes. Is there any way I could retrieve the 20% (or a part of it)? I used to pay my taxes as required when I was working/living in the US but have not filed since.

No - remember that a 401(k) paln is actually a deferred compensation plan. So when you take a withdrawal you are essentially being paid the salary you deferred, plus earnings that have grown tax-deferred. Since you didn't pay taxes on this money when you first earned it, now that you're making a withdrawal the tax bill becomes due. There is no free lunch.

Ah, was wondering if the 20% was residency based. Appreciate the response.

No, the 20% is actually just a down payment on the tax that will be actually due.

Given the 10% Early Withdrawal poenalty plus regualr taxes due, it could be as high as 45%.