That depends on whether the modem came pre-installed in the Dimension 4100 or whether it's an add-on product.
If it came pre-installed in the Dell machine then Dell would support it. However, in checking the Dell website, they make no mention of this machine coming with a Netodragon modem installed.
If it's a retail add-on product, then you must get support from the manufacturer.
Netodragon was taken over by Pro-Nets Technology Corp. This is their website url:
http://www.netodragon.com/
also read the info posted in this thread:
http://forums.driverguide.com/showthread.php?t=24895