When the Finder opens or closes an item, it shows an animation effect usually called the "ZoomRect" (zooming rectangles describes it pretty well, so that's what those innovative programmers called the procedure). When you open or close a lot of items, especially on a slow Mac, this effect is suddenly renamed "damnSlowZoomRect". Here's how to remove the effect:

1. Open a copy of the Finder with ResEdit 2.1.1
2. Open the Code resource
3. Open Code ID 4 (Yup, you need to decompress it)
4. Find hex 4E56 FFE0 48E7 1F38
5. Select these bytes
6. Replace with 205F 700A DEC0 4ED0
7. Save the copy of the Finder and close ResEdit.