You may experience the 'Blue Screen' error messages due to a hardware or a software issue. I recommend running hardware diagnostics to check for the hardware functionality. You may find the following steps useful:

It could be annoying when the DVD drive disappears after boot up. I suggest you to run the hardware diagnostics as you also reported about USB issues by following the steps provided the link below: http://dell.to/OUGnqT Please reply to this message with the results of the diagnostics.

This problem only started today. I was trying to download a file using Firefox, nothing unusual there, but as I was doing so volume display symbol, i.e. the one that appears when using Fn F11 or F12, kept appearing and flickering.