You really should not be using SP4 on NT; it has far too many IP based problems, and also introduces timing problems on multi-processor machines. Most places I know using NT nave gone directly from 3 to 5. 6A is actually better, but introduces problems itself. There are a number of online articles in the M$ knowledge base regarding multi-processor problems resulting from the application of SP4. Sorry, I have no reference to hand.

IE3 illegally modifies kernel DLL sets, and given that IE4 is buggy and unstable (plus bulky in the extreme) you should dump it an go to 5.

One of the few remaining Mk1 owners... #00015