I have verified that the 10/3/15 400.vps virus database (version 151003-1) does NOT work with Win98.

Also, I have found that 400.vps is a compressed file. So the 10/2/15 file (version 151002-2), the last that I found that worked, is actually probably 250Mb+. It seems that Avast4.8 holds the extracted 400.vps in RAM and in the Swapfile: I haven’t been able to find a file with a filename on the hard drive. I’m guessing this is where Win98 fails, trying to extract (expand) 400.vps

The link that GreenEyedLady left for the 9/11/15 vpsupd4 no longer works. The archived snapshot depends on the source’s permission to use it. Did Avast revoke the permission? When I traced back her link, I found vpsud4’s dating back to 2010. About one every 90 days.