CD/DVD ROM disappears

I have the following problem.

First, I thought I had problem with power supply, so I changed the power supply. This is not the problem. When I boot my computer I sometimes see my SAMSUNG CD/DVD-ROM (2-3 years old) is not detected (black/ empty secondary slave position). I have not set any jumpers as these should be no need for that. But sometimes it is detected and working completely NORMAL. In windows, 50% of the cases my CD-ROM works COMPLETELY FINE, but after 5-10 minutes I get the message that my CD-ROM is unplugged and it completely disappears from windows. But when I press the eject button to test it the CD-ROM ejects nicely. It seems the CD-ROM somehow disconnected from windows (2000).

I thought I had bad power supply, but this does not seem the problem.