If you've upgraded to Quicken 2010 and notice that your .QDF data file has increased in size, here's why:

Unlike earlier versions, the data file structure for Quicken 2010 for Windows no longer contains separate supporting files. (Supporting files have file name extensions like .QEL, .QPH, and .IDX.)

Instead, the supporting files have been incorporated into a single Quicken data file with the .QDF file name extension. This simplifies the Quicken file structure and—as expected—makes it larger.