Well, in experimenting, I believe I found an ideal solution for you. First, set the max menu height. To do this, Right click TLB, select "TLB Settings...", and click "Metrics" in the left-hand pane. In the right-hand pane that comes up, there's an option for max menu height at the top right. You can change this number to any value between 200 and your screen's Y resolution (1024 in your case). When you are done, click "OK". Next, you need to tell your menu to use two columns. To do this, right click inside the menu you want to cange, and select "Customize Menu...". Make sure "Options" is highlighted in the left hand pane, and you should see a blank labeled "Columns:" in the upper right of the right hand pane. Change this value to 2 and hit "OK". It would be a good idea to refresh TLB at this point (right click on TLB, then "Refresh").
If done correctly, your menu will be a single column untill it grows taller than the value you set for max menu height, at which point it will split into 2. If your menu is taller than double the max menu height, you can scroll through, but personally I don't like the way the scroll works in multiple columns. Hope this helps.
WinXP Pro (5.1.2600) SP1 TLB 3.0 IE 6.0.2800.1106 Shell 6.0.2800.1106
Command Line 3.3.0.0 Process Viewer 2.0.0.0 Calculator 1.0.0.0
Weather Forecast 1.0.0.0 Media Control 4.0.0.0 Volume Control 2.1.0.0
Net Monitor 1.4.0.0 Up Time 2.1.0.0 System Monitor 2.4.0.0
Drive Space 2.3.0.0 Mail Monitor 1.9.9.0 TLB Clock 1.3.0.0