As Rob said, you need a cross-over cable if connecting directly to the computer. But I vaguely remeber having problems connectting directly to some 100Mb/s adapters (and to others not) - link continuity lights were on on both sides, but the beasts did not want to talk. So, if after trying with cross-over cable you still have problems, consider a cheap 10/100 switch or even an ancient 10Mb/s-only hub if you have it in some junk heap (with 'ordinary' cables, of course).