Hello AM,
Officially: No. The upcoming 2008 release of Visual Studio will support this
for framework versions 2.0, 3.0 and 3.5. Microsoft calls it multi-targetting.
The reason for not supporting version 1.0 and 1.1 of the .NET framework in
2005 (and 2008 for that matter) is that due to extensive changes to the Common
Language Runtime they would need to provide 2 seperate versions of many of
the parts that make up visual studio (COM wrapper generation, Debugging,
ASP.NET Designer etc).
As far as I can tell Microsoft will not release a version of Visual Studio
that will target the 1.x versions of the framework at all. There is an unsupported
add-in for visual studio 2005 though, called MsBee, which allows MsBuild
to compile using the 1.1 compiler. I haven't used it till now, but it might
do the trick for you.
Jesse