Yes in deed it is.
I`ve been hearing for quite a while that the performance actually decreases on older cards, when the newer drivers are installed, yet I`ve never heard of a problem that is similar to yours... Eh, I don`t remember if it was like that with the Riva`s, but the GF`s aren`t made by Nvidia itself, yet by different companies, i.e Leadtek, Hercules, etc. Try and download the drivers that are released by the company that has built your card, maybe it will work.