in windows xp on ntfs file system there is an option to seem-less compression of files "on the fly" by the file system.
may be some time you should do it again. for new files.
because it seems that windows do not make new files compressed automatically.
but those that already marked as compressed they still save space( like common log files).
my metatrader folder was 3G and after that it became 1G and the charts load faster.