Now back on original RAM and computer booted OK from hard disk. I tried various combinations of the ram. In all cases I could boot into dos and using the rescue floppy could access the cdrom. I tried to reinstall w98 and in most cases got thro scandsk ok but in all cases the machine stalled while loading w98 setup with some some screen corruption. I suspect the new ram may be too fast for the system. The strips are coded MS3828UPM PC133 NO Rip for valid RMA. TA for replies.