Cd/dvd will not play

If it's the caddy type drive (that can be removed completely from the laptop) try removing it and reinserting it.

You may have inadvertently dismounted it via the safely remove process if you recently removed a memory stick that way.

Also go Control Panel, System, Hardware, Device Manager and see if the drive is missing or listed, disabled or yellow flagged as faulty.

Also look at this:
http://support.microsoft.com/smarterror/default.aspx?spid=global&query=kb%20314060%20p%201&errurl=%2fdefault.aspx%2fkb%2f314060%3fp%3d1