I did exactly what you suggested. In attempt 1, the configuration was:
Slot A2 .....1 GB
Slot A3......1 GB
The PC booted up all right but when I ran Belarc Advisor, only 1GB was detected and slot A2 showed as empty.
In attempt 2, I removed the card from slot A3, leaving only 1GB in slot A2. The PC would not boot up and there was a long intermittent beeping sound.
Finally, my current working configuration is:
Slot A0 ...1 GB
Slot A1....1 GB
Slot A3....512 MB
The above is recognized by the system.
I will be glad for any further advice/comments.