Windows Explorer (the file explorer, not Internet Explorer) is missing a key feature: The ability to asynchronously count up and display folder sizes without pulling up the Properties view. This proves quite important when trying to track down what directory contains big, bloated files. Someone created something for this, though, here:

http://foldersize.sourceforge.net/ 

I tried it on Windows Server 2003 R2 and it just works; it causes Windows Explorer to just add the column as a column option (choose columns).

Unfortunately, however, it doesn't work with Vista. Why? Because Microsoft killed the Win32 API call for it. Apparently, they replaced it for file metadata support as is found in MP3 files. (Garbage. OK, this is stupid. I'm becoming a Microsoft basher now?) http://foldersize.sourceforge.net/vistasucks.html

I sent a $15 CAD donation to ask the developer to continue to look into a workaround for Vista.

Update: He sent me an e-mail and said he wants to focus on Ubuntu. That makes it a different product altogether; essentially, I take it as "no, I won't support FolderSize for Windows Explorer anymore". Quick, Windows Vista users, send him more $$!!