Intel E100B driver you gots?
Anything before 6.1.1.0 has got some serious problems when used in Auto-Negotiation mode when connecting to SOHO class Hub/Switches/Routers (IOW Unmanaged), especially with some of the newer 10/100/1000 switches popping up.
6.1.3.0+ (6.2.1.0 is newest I think) actually has a firmware workaround for W2K and XP. Dunno about Win9X... ancient history... I know... 65% is still @Win9X
This bug also affects the E100+, E1000+ Copper, E100+ Server, E1000+ Server Copper. It doesn't affect E1000SX/LX/ELX Fiber NICs though...
SO update those NIC drivers... I am guessing since I actually pay attention to Intel NICs and the development of them... kinda nice for you all... ;)
BTW, this bug doesn't affect the "Stock" Kernel Module, or the Source version from Intel.. as it was fixed LOOOOOONG ago. Linux tripped on that one kinda hard... since it CAN utilize a 100Mbit pipe to nearly it's theoretical max...
BTW, I believe 6.1.3.0 is the newest version run through WHQL Certification... YMMV, but I'm running versions all over the place in Winbloze.