Wendell is right. They were wrong
As a side note: 4GB of DDR3 is 20 bucks. 8GB is 40 bucks. No reason to not get 4GB at least. Unless they have it on a 32 bit system which typically uses 3.3GB of that 4GB. Gamers on 32 bit systems (scarce nowadays) use only 2GB since their graphics cards like to take 1GB of that 4GB limit on 32 bit systems.
They rationalized that since that server CPU wasn't doing anything but running the amazing charts database, that the ram shouldn't be an issue.
It's not just storing the database. It's actually running SQL server which likes that 1GB of RAM. It's doing all the searching and look ups when you run a search for a patient. The more of the database in RAM, the faster it can look up stuff since it doesn't have to search the hard drive. The processor helps too since it can process the commands quicker and return the results to your database query.
This another reason why we recommend keeping a dedicated computer/server for AC. If you load any viruses or mess something up on your own computer which has the database, the consequences can be severe.
Also as a side note, it's a bad idea to run multiple installers simultaneously.