Is there a way to set up a default folder for Windows Explorer?

Edit the following registry subkey:

HKEY_CLASSES_ROOT\Folder\shell\explore\ddeexec

If you change this subkey's default value to [ExploreFolder("yourNetworkDrive", yourNetworkDrive, %S)], you force Windows Explorer to start at the drive you specify.

Replace yourNetworkDrive with the drive you want. If the drive is mapped as S:, the string would be [ExploreFolder("S:\", S:\, %S)].

To present a single-pane Windows Explorer view, you can change ExploreFolder to ViewFolder.

To change the default setting so that all top–level drives and folders are shown, follow these steps:

1. Click Start, point to Programs, then Accessories, then right–click Windows Explorer, and click Properties.
2. Under Target field, which reads %SystemRoot%\explorer.exe, add to make the line read %SystemRoot%\explorer.exe /n, /e, /select, C:\
3. Click OK.

source

I actually use a utility called WinKey to do something similar to this, without rerouting Win+E. I'm sure AutoHotkey could do the same thing. In fact, having said that, I think I just made some work for myself. :)

In WinKey (or soon, in AutoHotkey) I mapped Win+W to open a Windows Explorer window rooted at my standard "workspace" (thus, +W). This way I retain the standard Win+E, which I also use extensively, and right beside it is the hotkey to open my workspace.

OK, work's done. Here's a simple AutoHotkey script I'm now using for Win+w to open my workspace:

#w:: ;; Win+w
{
 Run C:\WINDOWS\explorer.exe /n`, /root`, C:\workspace\
}
return

The command's commas are escaped with a backquote. Replace C:\workspace\ with whatever folder you want to view. Replace "/root" with "/select" if you want two-pane instead of single-pane.

Another example of autohotkey script here