e-Machine is now owned by Gateway and represents a line of entry level desktops. You will find them at WalMart for less than $500. IIRC they utilize Celeron processors (not great for gaming) and expandability is limited. That said, I own an eMachine laptop built around an AMD Duo Core processor and it's been relatively trouble free.
Bottom line, if your parents gave it to you, say "thanks" and enjoy it. If you're thinking about buying one, save your $ for a home built.