For the first option, create a default.asp page on the root  directory with
the following ASP code

<% Response.redirect "/workspace" %>

For the second option, try creating a new web site that point  to a directory
with a different default.asp with the same code as below. Not sure it will
work but worth a try

The above tip worked great for me.

Or use next one

msdn.microsoft.com/.../
dnmsipag/html/msi_pag_chapter6.asp

Configure Redirection to the Workspace
Redirection enables users to navigate to the corporate portal  without having to
know the name of the workspace. For example, if the server  is named CorpPortal
and the workspace  is named Home, a user could then navigate to the site by
typing http://CorpPortal instead of http://CorpPortal/Home.

To configure  redirection

On the taskbar, click Start, point  to Programs, point to Administrative Tools,
and then click Internet Services Manager.
Expand the server node.
Right-click Default Web Site, and then click Properties.
Click the Home directory  tab.
In When connecting  to this resource, the content should come from,
click A redirection to a URL.
In Redirect to, type /workspace_name
In The client will be sent to:
Select the The exact URL entered above check box.
Select the A directory below this one check box.
Select the A permanent redirection for this resource check box.
Click OK.