It's absolutely boring to navigate to your most often used folder in windows save or open dialogs. Th purpose of Places bar is to help you to do this faster. The Places bar locations can be edited via Group Policy editor in Windows XP Pro and Vista. Use the following way:
1. Open gpedit.msc (Start->Run)
2. Navigate to User Configuration -> Administrative Templates -> Windows Components -> Windows Explorer -> Common Open File Dialog
3. Open "Items displayed in Places bar" and write down the locations you want with their paths. Symbolic names are also allowed like Desktop.