Optimize Apache for large file downloads Options

I originally posted this in alt.apache.configuration , but after
searching more on the Apache pages, perhaps this is the correct group.

Hello,
We have an in house http based records system at my company. Several
years ago I converted it from running on IIS to Apache. Everything
has
worked perfectly. The server has to be Windows for a variety of
reasons. Apache 2.0.45 was latest and greatest at the time, so that
is
what I have been using. The files are uploaded using a cgi/http post.
They are downloaded using straight http. All files are zip
compressed.
We have started storing some larger files within the application.
Some of the files are now 50 MB and greater. For my benchmark on this
issue, I'm using a 47 MB file. As the files grew, the download time
has become slower than I would have expected. On the 47 MB file, it
is
between 12 and 15 seconds every time. Given the number of files a
user
would pull over a day, this actually really adds up. To simplify
troubleshooting, I just did a fresh install of the newest windows
Apache with all the default options. It still takes 12 to 15 seconds.
Now for the fun part. IIS 6 on the same server, download time is 3
seconds. It is reproducible on different machines. The servers are
New
HP DL360s with plenty of horsepower. It is a gigabit LAN. 2003
server.
Straight Windows file copy takes about 2 seconds. I really don't want
to have to go back to IIS. I'm sure there has got be a way to
optimize
my Apache configuration to speed it up. I can't imagine IIS being
faster. I will be glad to provide any more info that might help.