In comp.security.misc Zak <duff@nomail.invalid> wrote:
> Has anyone kept a running total of how many MB of download have been
> needed to keep patching XP ever since its launch? It must be some big
> figure.

Well, if you wanted to spend some time, you could get a rough estimate
by using the security bulletin search:

http://www.microsoft.com/technet/security/current.aspx

You can search that based on product (eg XP) and service pack installed
and it should return all security bulletins for that product that are
not covered by the service pack. Then total all the download sizes, add
in the size of the service pack and you have your rough estimate.