My Camera Mate parallel external PCMCIA/CF reader works fine on an HP Pentium 4 under NT. I can hot plug/unplug to my hearts content. However, it's slooooww.
My Lexar Firewire external CF reader works great under XP. Again hot plug/unplug is not a problem and it's very fast. However, you need a $30 Firewire card obviously for a PC. Works great on my Mac laptop too.
I also have a USB reader that seems to work fine now under 2000 but initially hot plug/unplug was unreliable for some reason.
I've seen IDE 5.25" bay PCMCIA readers on the net, but so far I've never ever seen anyone with one in stock.