I need to upgrade the video memory on CP765V2 PCI VGA Card from 1MB to 2MB?

Please add the memory the same as original (on board). Be aware of the name of video memory board and the speed when you add the video memory.

I can't run DOS games with this card and the Win95 system will freeze occasionally.

The correct S3 CP765V2/LV2 chipset is Tiro64V2/DX. You should choose the "Trio64V2 DX/GX" driver for this card. You can get this driver from the CD-ROM in the S3_TRIO directory.