Copy/Paste
copy the desired brushes from Program files/Adobe/Photoshop7/Presets/Brushes and paste them into Program files/Adobe/Photoshop Elements/Presets/Brushes

Next, in PS Elements, click on the preview-button of your brushes, click on the tiny arrows on the right of the 'overview'-window of the brushes, click on Load Brushes and load the brushes from the Brushes folder (as mentioned above).

Good luck

PS in fact, you can load the brushes from the Photoshop folder too (so without copy/paste)