Some of IIS 6.0's settings can be set "globally", like the default start path of the log files. See this article on TechNet:
Changing Default Web Site Settings (IIS 6.0)
However, some of the settings you change will not affect your existing webs. For example, if you set the default path for your log files, this won't change the folder for your existing log files.
During IIS installation, default
values are set for the various
properties assigned to Web sites.
Properties can be set at the global
level, affecting all Web sites on a
server, on the individual site level,
at the directory level, or at the file
level. IIS uses an inheritance model,
which means that settings on higher
levels are automatically inherited by
lower levels. Settings at lower levels
can be edited individually to override
inherited settings from the next level
up.
If you change a setting at a lower
level, then later change a setting at
a higher level that conflicts with the
lower level setting, you will be
prompted to choose whether you want to
change the lower-level setting to
match the new higher-level setting.
Regarding the home path of new web site: if you create a new web site, the IIS wizard will always prompt you for the path.
If you have to migrate your files to a new folder, I would do it one-by-one (if you don't have hundreds of them - then some scripting would be necessary). Be sure you test the sites and check if there are directories which needs "special" permissions.
Best Answer
The default is indeed to not have content expiration enabled on the server. This doesn't mean that no expiration is happening though, just that the client will control content expiration.
You can enable it for all sites/virtual directories by going to the setting at the "Web Sites level (in IIS6) or at the server level (in IIS7) - this will make the setting propagate down to all existing sites and be applied to any new site.
This doesn't "keep the setting enabled" though - any site or virtual directory could potentially have its own custom setting for content expiration.