Acer Aspire 5610Z CD/DVD Rom troubles

I have an Acer Aspire 5610Z that i purchased from walmart as a personal laptop for school. It runs Vista.

Recently my CD/DVD Rom was malfunctioning. It would show up in my hardware information one moment, then dissappear (for lack or better description).

This happened for awhile and i was told by a friend that a Trojan or a Virus had infected my computer, but none of my anti-virus could detect that my system had any such infection. Now it is not showing anywhere on my laptop, though it still has power and still runs.

Can anyone help?