This solution uses a similar technique as InjuryProne19's, but it'll be made automated so you'll only actually have to win ONE
game, as opposed to 100. The last 99 will be won by the computer.
First things first, you're going to have to download TinyTask, which is a program that allows you to record a series of mouse movements and button clicks and play them back continuously, automatically. You can download it here: http://www.vtaskstudio.com/support.php
Once it is installed, run it and load up a game of FreeCell. Now, in the TinyTask options menu, change the recording hotkey to F8 and the playback hotkey to any one of the other options. Head into the FreeCell game and hit F8 to start recording.
Now that you're recording, here's all that you're going to want to do:
1) Click on the "Menu" button.
2) Click "Game Options".
3) Type "10913" in the text box.
4) Hit "Play".
5) If a tutorial pops up, hit "Close". If it doesn't pop up, then skip this step.
6) Complete the game. For this, you're going to want to do these moves:
5 of Diamonds -> 6 of Spades
4 of Clubs -> 5 of Diamonds
10 of Clubs -> J of Hearts
8 of Spades -> 9 of Hearts
9 of Diamonds -> FreeCell
J of Hearts -> Empty Column
7 of Diamonds -> 8 of Spades
6 of Spades -> 7 of Diamonds
6 of Diamonds -> FreeCell
6 of Hearts -> 7 of Spades
5 of Spades -> 6 of Hearts
4 of Hearts -> Foundation
5 of Hearts -> Foundation
4 of Diamonds -> 5 of Spades
8 of Hearts -> 9 of Spades
Q of Hearts -> Empty Column
K of Clubs -> FreeCell
Q of Clubs -> FreeCell
9 of Spades -> Foundation
7) Click anywhere on the board once the ending animation starts.
8) Click "New Game".
9) Once the cards are dealt, hit F8 to end the recording.
Now that you have a recording of you winning a game, in the TinyTask options, change the recording hotkey to another button (any button that is different that the one you have set for the playback hotkey), and then change the playback hotkey to F8. You're also going to want to turn on "Continuous Play". Now from here, go into the FreeCell game and hit F8. It will then start playing through games over and over again. After a few hours (the time it takes depends on how quickly you won that game), it will finish its 100th game and you will get the achievement.
You will also unlock:
(Assuming you didn't already have it).
As well as:
(That'll unlock after just 10 games. It won't take nearly as long).