The only (potential) problem I see is that, for some reason, Apache thinks that a .chm file is a “chemical/x-chemdraw” file. But as soon as you save the file, the MIME type doesn’t matter anymore, as Windows does only look at the extension.
tw@kwlinux:/tmp$ wget http://www.mairlist.com/download/mAirList/v3.0/scriptinghelp/mAirListScript.chm
--2010-02-11 19:12:35-- http://www.mairlist.com/download/mAirList/v3.0/scriptinghelp/mAirListScript.chm
Resolving www.mairlist.com... 85.214.99.225
Connecting to www.mairlist.com|85.214.99.225|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 481215 (470K) [chemical/x-chemdraw]
Saving to: `mAirListScript.chm'
100%[=============================================================================================================>] 481,215 567K/s in 0.8s
2010-02-11 19:12:36 (567 KB/s) - `mAirListScript.chm' saved [481215/481215]