[newbie] I can't detect my modem

[John]

It is on com port 4 in windows which is ttys3 in linux I believe.  When I query it using KPPP it tells me "Sorry, modem is busy".  Of course it also says this for just about every other port as well.  I found some documentation on Maximumlinux.com and it mentions that special instructions are required for ttys2 and ttys3.  Of course they don't tell you what these instructions are.  I am unable to change the com port to 2 as it goes to 4 automatically when it installs (in Windows).  I am really stumped here.  Any words of advice?  Thanks   John