Explorer with Tabs (That's Windows Explorer, not Internet Explorer)
INFO SCIENCE: Here's a great new program I just started using. Direct from the horse's mouth:
ExplorerXP is a very fast, small, compact and innovative FREEWARE (for non - commercial use) file manager for Windows 2000/XP. Unlike the regular Windows Explorer, it displays the total size of each folder and allows you to browse multiple folders from a tabbed interface.

What does Microsoft have against tabs anyway? We may never know.
Now all I need is an explorer / desktop / interface for XP that looks and works like my Powerbook does and I'll be golden.