I was reading a feature on the traktor (pc mixing software) website on matt black from coldcut and he said he uses -
Dell Inspiron 8000, 866 mhz, Win2k

he then went on to say this about soundcards with this laptop :-

(I am now using a ) Roland UM2. Despite much effort have not found an ASIO sound hardware solution that works well on the Dell. Tried MOTU 828, Wami Box, Emagic 2-6, Digigram VXpocket. All have problems.

So it seems you're not alone. Personally if i had tried that many soundcards I would get rid of the dell....but I know it's not quite that simple!