Forum Moderators: phranque
Welcome to WebmasterWorld [webmasterworld.com]!
For a site re-design, I'd question whether you should use a 301 redirect in most cases. Simply map the old URLs to the new filenames as closely as possible using internal rewrites at the server level, and then 301 redirect anything that is left over. One of the concepts that's worth getting used to is that URLs and filenames need not have any specified relationship. On many sites, they do -- or they appear to, but this is not necessarily the case. For the sake of search engine rankings and of your loyal users who have bookmarked your pages, you should avoid changing URLs if at all possible.
So, if you changed your site technology from .html to .aspx, there's no need to change URLs at all: Simply 'map' all .aspx files to the old .html URLs, and carry on.
For changing a domain name, a 301 is definitely the way to go, as it tells the clients (most importantly in this case, search engine spiders) to drop the old URL and use the new one in the future. Since you're changing the domain name, the URL has to change in this case.
All that said, I'll have to confess to being an Apache guy, so I can't claim any expertise on IIS implementation. :)
Jim