I'm not sure if the driver version you're referring to ever existed for windows 98, it may have been an XP only thing.

https://www.nvidia.com/en-gb/drivers/win9x-archive/

https://www.gigabyte.com/Graphics-Card/GV-N62256DP2-RH#ov ...looks like XP only

On the other hand, for some reason it is very hard to believe that ALL THREE independent sources are lying at once. Yes, and photos of the original GIGABYTE CDs for these video cards, on which support for 9x is clearly indicated, makes you somewhat doubtful. Unfortunately, we won't find out the truth until we find this disk.

Here are more examples of photos of such CDs for Gigabyte 6-series video cards, where the presence of a driver for Windows 98 is explicitly indicated:

128Mb <PCI-E> DDR2 GIGABYTE GV-NX65128D (OEM)64bit D-Sub+DVI+TV Out <GeForce 6500>
https://www.nix.ru/autocatalog/gigabyte/video … 3.html#pid=2247
https://static.nix.ru/images/gigabyte-gv-nx65 … ft&view_id=2247

256Mb <AGP> DDR2 GIGABYTE GV-N62256DP2-RH (OEM) 64bit DVI+TV Out <GeForce 6200>
https://www.nix.ru/autocatalog/gigabyte/video … 9.html#pid=2247
https://static.nix.ru/images/gigabyte-gv-n662 … ft&view_id=2247

256Mb <PCI-E> DDR2 GIGABYTE GV-NX66T256DE (RTL) D-Sub+DVI+TV Out+SLI <GeForce 6600GT>
https://www.nix.ru/autocatalog/gigabyte/video … 7.html#pid=2247
https://static.nix.ru/images/gigabyte-gv-nx66 … ft&view_id=2247

256Mb <PCI-E> GDDR3 GIGABYTE GV-NX68G256D-B (OEM) D-Sub+DVI+TV In/Out+SLI <GeForce 6800GS>
https://www.nix.ru/autocatalog/gigabyte/video … 7.html#pid=2247
https://static.nix.ru/images/gigabyte-gv-nx68 … ft&view_id=2247

It turns out that even on later revisions of disks (Up to version 4.1), they kept a mention of Windows 9x support. And this is most likely not an error. And although none of these disks can be found on the Internet anymore, the first one is still interesting (For GeForce 6500\6200LE), because there is a high probability that the driver you are looking for is there.
Maybe there is some website on the Internet where collectors of old video cards live, from whom you could ask about the presence of such CDs in their extensive collections?

I do have the driver CD for the gigabyte 6600GT. Never thought to upload it as the drivers are already online.

I know The 6000 series does support windows 98. I forget which version added support, last 81.98 should work.
There was no 76.45 version for 98 as far as I can tell though.

Nearest version for 98 that I am turning up is... https://www.techspot.com/drivers/driver/file/ … formation/5437/

I wonder what version is on your CD and what exactly it looks like? It is known for certain that they soon removed Win9x support from later CD releases (removing the mention of 9x from the cover). Another caveat is that the GeForce 6600GT (NV43) and GeForce 6500 (NV44) were released with some time difference. Therefore, it is quite logical that the GeForce 6500 is equipped with the most recent and up-to-date driver at that time, since 77.72 did not exist at that time under 9x. The Internet archive, unfortunately, did not save the download page for GF6500\6200LE, but for all other cards under 9x, 76.44 from other 6-series cards was relevant for a long time, until the release of 77.72. 76.45 may not have been available for download, but it may have been available exclusively on CD. It is very unlikely that three people from different parts of the world made the same typo at once. What evidence suggests otherwise? In any case, only the real owner of the GeForce 6500 with the original CD, as in the first picture, will be able to put an end to this issue.