Modem Update Problem

[Charles Medler]

I am (trying) to help a friend get his recently purchased, slightly 
used iMac set up in his office. (See below regarding "slightly used") 
Running Jaguar, when we attempted to connect to his dial-up Earthlink 
account, we failed and got exactly the alerts and error indications 
identified at http://docs.info.apple.com/article.html?artnum=106575, 
namely
an alert box: "Internet Connect could not open the communications 
device"
and the following message in the Internet Connection Log:
"Failed to open /dev.cu.modem: Device busy."

(We are unable to check the third symptom, that the modem works under 
"pure" OS 9, because his iMac is one that no longer has an OS 9 startup 
folder option.)

So, delighted, I download the MacOSX ModemUpdate.pkg to my computer, 
burned a CD, loaded it into his machine, clicked as instructed and was 
greeted with a message saying that I couldn't install this update 
because it is already included in the installed OS X.

Regarding "slightly used": The computer had been returned to the store 
by its original purchaser for some unknown reason and my friend bought 
it for about $200 off the going price. Although the store guaranteed a 
complete system, that wasn't quite the case - at least with regard to 
the installed software. The OS 9 system folder had been removed along 
with Appleworks. We corrected that by running the Software Restore 
disk.

Any suggestions?