Due to stupidity, cornerstone does not provide all the drivers for the 20/70 in the same package, this zip has cornerstone's files and the driver found on driverguide, together you can correctly install your Image Accel Color 20/70. It even works on millenium [I'm using it now] Good luck.
The following files are found inside the driver download file.
|CD17_93.ICM||560 bytes||28 Jul 1998|
|CD17_65.ICM||560 bytes||28 Jul 1998|
|CD_50.ICM||560 bytes||11 May 1998|
|c20-70.INF||4.4 KB||28 Nov 2000|
|CD_65.ICM||560 bytes||11 May 1998|
|CD_93.ICM||560 bytes||11 May 1998|