Read this good article on windows nt/2000/xp/2003 cache feature http://www.heise.de/ct/english/97/01/302/, if you notice the date, then you will find out that this bug still exist until this day (maybe until longhorn).

The solution for this is periodic cache resetting tools, like on www.sysinternals.com.
The progress corp should use FILE_FLAG_NO_BUFFERING when opening database file for its next progress version.

I think that right now my huge database (4GB) file is using two memory cache. The first one is progress buffer which can be changed by -B parameter. The second one is Windows cache that steadily grow to as large as my frequently used file, that is 4GB database (yeah, nice algorithm, cache frequently used file, but with no stoping ?). I don't know a way to turn off windows systemcache/filecache/pagecache. Maybe hacked windows do.
Without cache resetting tool, my initially 1.5GB free will become 10MB free after few weeks. When restarting server is not an option, what will you do ? I appologize to all users every monday morning before I use auto cache reseting tools.
Anybody have better solution ?
I use Windows 2000 Advanced Server SP3 with Progress 9.1C DB.
I think other database experience the samething on Windows.
I can't use BSD or Linux because of third party software requires it.