Hello pj. Is this a Windows-style pop-up or is it generated by your adapter's software? (This is on your Win 98 PC, yes?)
A non-selective approach is to disable balloon notifications, which will apply to any program that uses them, but I'm coming from an XP perspective and I honestly don't know whether 98 has the same ability. In XP, I use TweakUI to remove the balloon tips. Perhaps the 98 version of TweakUI (if you have it) has an equivalent.