is a good place to find out the ram
www.crucial.com
And as for harddisk, most are 2.5" size, some goes smaller with 1.8". Yours will be 2.5" However, having problem finding with your a200-series model, thus, unable to tell yet which connection type is yours (SATA or PATA/IDE).
I have a toshiba satellite a200-s500 and want to upgrade ram and eventually hard drive to boost performance and capability. I read one place that the ram can't be upgraded, then another person wrote it can be bumped to 3 gb. Also anyone know what size hard drive it has(2.5" or 3")? I don't have manual. Figure I will get the correct info here. Thank you for any and all asisstance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic