I have a Dimesions XPSB733 and have recently been encountering some problems and I think it might be the harddrive going/dying.   I will sometimes get ready to go on my machine and will see a black screen with a small blue box somewhere on the screen.  Nothing can be done at this point, so I restart the computer and when I do I get to "No boot devices were found-System Halted".  I am running XP and recently upgraded memory to 512mb from 128mb.  One suggestion I found on the the Forums was to reinstall the new memory and then try to restart.  That DOES work if I do that for a little bit, but it is quite frustrating to have to do that basically every day now.  Could it be that my harddrive is going bad??  The computer is about 4 years old.  Please help!!!