That's a very long message in which you never actually mentioned what kind of RAID you're using. If it's RAID 0, see this article (which Google found in 0.13 seconds):
Do they have Google in your country?
You may or may not be aware that the Dell 420 has been having problems with its RAID array. I wasn't when I bought it. Some kind of conflict with the Intel controller or some such. At any rate, it's full of all kinds of bugs.
Dell do claim to have offered a fix for the RAID problem (a driver download), but I (and a lot of people) have discovered it just doesn't work.
I've spent about five hours on the helpline today, talking to fifteen different technicians who just kept passing the problem to someone else until I was cut off. When I rang back and shouted at the first techy I spoke to (who had an irish accent and spoke clearly, as opposed to the inaudible indians) who eventually told me to revert the thing to factory settings. In between, we tried pressing the restart button for twenty seconds, reverting to an earlier version, launching start up repair, and repairing Vista with the disc, leaving only this option.
Since the problem has been in the computer since it arrived with factory settings, I don't see how this would help (and from reading around it seems like this fix doesn't actually prevent the problem recurring).
I then thought that maybe I could remove the RAID entirely (and use it as an opportunity to install XP instead of Vista, and thus avoid having to fix all its annoying featurettes all over again), but now I find that there's no option in the BIOS for disabling it at all. The BIOS only has options for "RAID Autodetect/ATA" or "RAID on"--both of which seem to do the same thing, neither of which switches off RAID. I also tried unplugging the hard drives on advice but still got the same BIOS screen.
So at the moment, I'm stuck with a terrible computer with a recurring crashing problem, that every couple of months destroys itself and forces me to spend half the day listening to Dell's awful awful hold music and inaudible indian technicians. There's no known fix for the RAID problem that I can find, and no way a novice like me can get rid of the RAID and just have two separate drives.
At least I've finally got it to start outside safe mode now--but the problem is just going to repeat itself and the error message on startup that the RAID is degraded isn't going away.
Is there anything left for me to do, or should I pack it in and buy a new one?