Regarding the various problems with PCI cards - sometimes it's
necessary to move them to other slots away from the AGP slot.

Regarding NIC settings - usually you don't have a choice to set it to
1000 mhz. While you do have choices to set it to 10 or 100 (half or
full) to get 1 gig you usually have to set it to auto. If you force 1
gig on wiring that can't take it, you usually won't get anything.

The NIC's I was putting in Win-98 machines was D-Link - DGE-530T
($26). During install I toyed with the settings and forced jumbo
frame size (8k). I backed it off to 4k and then got it to boot
properly into windoze.

Regarding switches, I replaced our old Intel 10/100 switches with a
D-Link - DGS-1224T - 24-Port Layer 2 Gigabit Switch ($400) about 6
weeks ago. All machines that have 1-gig NIC's are now operating at
1-gig.