Not quite all of them. Apparently out of all possible deals, about 1 in 100,000 is impossible to complete. The 32,000 deals in the Windows game include one such impossible game: number 11982. (I used to be so keen on freecell that I chose to include this number as part of my email address for precisely this reason). Two other impossible deals are also included as "easter eggs" in the game - to see them (and fruitlessly attempt to complete them), type -1 or -2 in the "select game" window.