Below is a list of modems that are not working in Puppy at present. If and when they are made operational they will be removed from this list and added to the list of working modems.
Alcatel/Thomson Speedtouch 330 (usb adsl modem)
DLink DFM-562I
ESS modems - not compatable with any flavor of Linux, including Puppy. (Mine is internal to HP Pavilion N5470)
Intel(R)537 Data Fax V.90 Modem
US-Robotics Performance Pro USR5610B
3Com Megahertz(R) 56K WinModem PC Card Model 3CXM356 (Note: Model 3CXM556 apparently works fine).
NetoDragon MDV92XP 56K (Conexant chipset) unless you use Linuxant.