Are you sure it's gaprhics card? 64bit is often mentioned as a system version (32bit and 64bit). System version doesn't mean THAT much for Morrowind, as it doesn't take advantage of 64bit systems.
But, if it's really a "64bit" card, then it is probalby it's memory bus. 64 is rather slow for novadays standars, but, as mentioned above, please find your exact model. If you are unsure about your exact specification, please post your laptop model - we'll find what we need.