alternatives
Not sure about Linpus, not least because I can't access there website currently, but if it is Fedora based, the yum command might be your best friend. "yum install thunderbird" should do it, if you have access to terminal.
Various reports I have seen suggest that Linpus Lite is not much fun, if you are doing more than internet browsing. The suggestions is often to install Ubuntu instead.
When it comes to AutoCAD, most people agree it will be tough to get it working with WINE, and a virtual machine will probably be pretty slow. I would at least look at http://lx-viewer.sourceforge.net/versions.php to see if it does what you need. If you just need to access dwg files, it might be enough.