Well... I also have one of those 4Mb ram cards and they do in fact speed ut the computer quite a bit (id guess somewhere around 2-3times). Everything done on the computer is somehow related to shifting memory or acting on it so fastram do a great deal even if it's a small program that don't use very much memory.
About the Harddrive you got... 4.1Gb is a perfect size, old FFS only handled 4GB harddrives (max 2Gb per partision).
