The ISA Supra Express 56i cards work, PCI cards don't. See: http://www.idir.net/~gromitkc/20010302a.html I have an ActionTec PCI call waiting card that works (It took a bit of tweaking, but their web page explains how). Generally speaking, external serial modems are "more compatible" , as are ISA internal modems. I have a useless Supra Express 56i USB. -Glen