How long ?
Usually not possible. It's already broadcasted


If you are in wrong blockchain(not updated, a few..), Just update wallet, and resync.

I disagree 

call HP to restore your lost data. Hope their price is not more than your coins

Related question for anyone who knows better than me: all you should need is the wallet address and the corresponding private key to access the coins in that address. Import the private key into a wallet and bingo, you have your balance back, just no transaction history.

Is this correct?

Do a dumpprivkey, make a note of it, and if you lose your wallet for whatever reason you can still recover?

Restore from backup. You have backups, right?

im using windows 8.1 and don't see previous versions in the properties tab for the wallet.dat file

If you're using Windows, you could try Properties > Previous Versions. I haven't tested it myself and I'd back up anyway before trying.

This is the normal course of events.  I predicted this, and profited by it.  MRO traded off-exchange rose 10x in two weeks, and when it hit the exchange, the initial inflow of fiat pushed it up 4x from there.  By 0.008 the top was obvious, and I sold half of my MRO.  I predicted a bottom at .004 but I was delayed in checking my computer, so I didn't start buying until 0.0027.  I think 0.0026 was the bottom, the end of a slide after one dead-cat bounce.  Now it is reboot time.  The weak hands have shaken out.  The miners who needed liquidity and/or have low long-term confidence in the coin (probably most of them, as miner's have other qualifications) have sold.  I am almost fully loaded again (and in fact have converted some BTC again, since I perceive 0.0026 to be a very very good opportunity).  Thus my actions attest that I think the bottom is in, at the 0.382 fibonnaci retracement level.  If I am wrong however, I will definitely add more (although probably I will recharge BTC from fiat as well, if I spend some on MRO, as I am uncomfortably low on BTC right now) around 0.00128.  I don't expect the next topping level to be lower than 0.0129, and I do not plan to sell any below that unless there is a transient spike, as any low liquidity environment is prone to admit, and I happen to be present for it.  I intend to add to my postion gradually until it meets my long-term goals.

(My conceit is that by smoothing out the volatility spikes, I add a valuable service, which aids in price discovery, and creates the humane reassurances of relative price stability.  Folks don't mind a gradual rise, but large sharp swings creates a kind of justifiable skepticism, and a degree of fear regarding where the price will be when liquidity is required.   "Gradual" is relative to the exchange history, of course.  I definitely find it enjoyable and personally lucrative to provide this service.  Probably I should spend more time writing code, and less time trading and talking.  I am not an MRO code contributor so far.  I am extremely well qualified to be one, however, at least technically.)

I would advise anyone (who is a friend, not an enemy) with discretionary investment funds to allocate a portion to MRO, because the chances are not bad that MRO will become the dominant privacy-enhanced liquidity vehicle of the coming decade, and in my estimation such a vehicle should command a market cap in the range of trillions of USD, once it reaches maximum penetration.  Even a small chance of such an outcome is worthy of attention in any rational portfolio.  On a time-scale of decades, the present price is largely irrelevant to the decision.  If you don't need to spend the money before 2020, then don't think twice about the price, just think about how much you want to lock up over that time (and the costs likely to arise if MRO proved to be the wrong vehicle, and you needed to switch horses) and then enter by dollar cost averaging.  It is truly hard to muck it up if you diligently apply dollar cost averaging.  If that is beneath you, you are a trader and have no need of my advice.

I personally currently aim to hold a long-term position of 8 BTC to 1 MRO, as MRO grows, as well as a short term trading position which is 10% of my crypto and fluctuates between MRO and BTC, in addition to my non-crypto investments (mostly swaps and spreads).  My risk tolerance is higher than most.

Remember that around 24k coins are being released per day. Absent significant developments over the next few weeks, the price will stagnate or even decline.

Is that code for, price has been down long enough. time to fire up the booster rockets, by any chance?

What's the point of placing a 8000 DRK sellwall, risking driving everything down and then just buying it yourself. Doesn't that just have an ambiguous effect at most ?