This evening, I finally tested HTTRACK a little time.
For your ASP problem, there should be a simple solution :

In the third page of WinHTTrack, there is a button "Definir 
les Options" (Options Definition).
Choose the "Correspondance type/MIME" and clear both Edit 
Zones which
contain "php,php3,asp" and " text/html"
That's all.

In the file <PATH_ON_HARD_DISK>\Name_of_our_Download\hts-
cache\winprofile.ini
this will clean these 2 entries: MIMEDefsExt1 and 
MIMEDefsMime1
. . .
MIMEDefsExt1=php,php3,asp
MIMEDefsExt2=
. . .
MIMEDefsMime1=text/html
MIMEDefsMime2=
. . .