What hardware do I have.

I have a Dell Dimension 8100 Pentium 4. Bios A09, Running Windows Xp Home Edition SP2.
Is there any software available that will tell me which "slots" inside my computer have "cards" or memory installed and what the "cards" are? I know how my system is configured, but I want to confirm things without opening the cover. I purchased the system with 256 MB Ram and now I have 512MB. I don't remember what the memory "layout" is now. It's been awhile since I've been inside the computer. I have a disability, (Stroke - Affecting my left arm and hand) and don't want to open up the computer just yet. Obviously, I'll do so before I purchase my upgrades, but I'm just comparison shopping right now.