You shouldn't. You only lost $10 by reformatting that pc - your only loss is from not buying the bitcoins at that point, of which most of us are guilty.
If you aren't in a pool the only way to get coins is to solve the block and in that case you would have had 50.
Any economy built on a currency that fluctuates this wildly is going to be unpleasant.
I don't know how someone can genuinely believe that bitcoin is a currency with this kind of pricing turbulence. It is behaving like the focal point of rampant speculation.
You might be wrong ;) This week, Yi Gang (a very high-ranked chinese government official: no less than the Director of the State Administration of Foreign Exchange and Deputy Governor of the People's Bank of China), said he would personally adopt a long-term perspective on the currency! See https://news.ycombinator.com/item?id=6782870
I got myself 3 or 4 coins (I wasn't even in a pool at that point) but then the price crashed in late 2011 and I eventually forgot about it. Since then I've reformatted and I remember having that "Oh shit" moment as I was reformatting but after looking up the price I realized I was only out about $10. This was late 2011.
Now every time I see a HN post about a new price milestone I kick myself. Today I could have sold them for ~$1500-2000.