Unplug the data cable from the back of the optical unit.
If it still opens......replace the optical unit.....20 buck item.
I have a 5-year old Dell Dimension E521 with an internal DVD+-RW TS-H653A SCSI CdRom Device and I run Vista. The empty disc drawer opens for no reason and when I shut it it just keeps opening. It almost always begins happening at PC startup (before I'm even in Windows) and continues sporadically no matter what programs I'm running (mostly IE and Word). I've run AVG, Malwarebytes, Superantispyware (all free versions) and defragmenter, with no change. Any suggestions? Thanks in advance.