Also how'd you like to be assessed for 400K when you'd be lucky to get 200K for it? Just think of the INTEREST you're also over paying in the inflated mortgage? WHEW!
If it was valued at $400K when the loan was taken out and the lender hasn't called the loan because value is $200K, and you make enough to pay the payments and live there, just what's the problem? If it was me, the first thing I'd be doing is getting on the taxman's ass and get him to drop my valuation too.
If on the other hand you were taking advantage of investment potential and NEED to sell the house at a higher-than-payed-for price, then you're screwed and might just have well bought a buttload of penny stocks...