Jsm,
Have you ever tried to get a PCMCIA card working on a laptop running DOS 5.0 and Windows 3.1?
I remember spending a few days trying to get a laptop running properly before Win95 came out. The hastle of playing with settings in the config.sys and autoexec.bat files is more trouble than its worth. Anyone remember memmaker and himem?
Teatowel,
For the spec of laptop you have got, I would install win98se. Its not too resource hungry, is fairly stable (compared to win95 or win3.1), has plug and pray - sorry - play

capability and has power management built in.
W2k is very good (I run it on both my laptop and desktop PC) but it would run like a three legged dog on you PC unless you can substaintially increase the memory (to at least 128Mb). Also you don't mention the size of your hard disk. W2k can take up a lot of disk space.
NT4 again is good, but as Rogue mentioned above, it lacks plug and play, and only has limited power management features. If you can live with that then it is a very stable OS if you have all the service packs and patchs installed and is secure. Its also not too resource hungry but could probably do with about 64Mb to run really nicely.
As I said above I would do a clean install of Win98se (maybe after getting the latest bios from Toshiba), get the latest patchs from microsoft, get all the latest drivers for the graphics card etc.
After that I would just make sure it is set up properly e.g. turn on dma hard disk access, turn system sounds off, don't use wallpapers, make sure only the programs you really need are running in the system tray, so turn off task schedular, turn off the infrared tool. Also, don't use the microsoft office toolbar (just put the icons on the desktop)

, take fast find out of the startup group menu.
Hope this helps.