NVIDIA has a driver archive on its FTP server - ftp://download.nvidia.com
. Look around there and there should be a folder for the 30.82 drivers. Those should be compatible with Windows XP.
I'm not sure exactly what you're trying to achieve with this card, but it's not going to be good for anything except maybe
Quake 3, and even that wouldn't be good for much above 640x480 resolution with low detail. The TNT2 M64 is bascially a gimped TNT2 Ultra, kind of like how the GeForce2 MX was a gimped GeForce2 GTS. Performance will be slightly higher than that of a TNT but far less than pretty much anything else.
Since you're asking about overclocking, I assume there will be some gaming done on this machine. Be advised that most every game released after Quake 3/Unreal Tournament (the first one) requires a card that can perform hardware transform and lighting, which the TNT does not support. As such, overclocking this card will gain you next to nothing. Even if it's a much older system, like a Pentium III-class, you should have purchased a card like a GeForce3 Ti or GeForce4 Ti4200. Those can be had on the cheap, (often less than $50) will give you performance that scales well with old processors and are capable of playing more modern titles.