capibarbaroja: First I need to clear up some terminology. When you are saying "reboot" I am assuming that you mean doing a "system restore" and not just restarting the computer, which is the typical usage for "reboot." You asked whether there was any way to restore the registry and there are two ways: System Restore and the Dell Factory Image Restore (that's the case for both you and I as I have a Dell also). The Windows System Restore restores your settings to a previously saved point (a restore point). That includes the Registry settings but does not affect any data that you have saved such as pictures, e-mail, etc. The Factory Image Restore is a last resort option when nothing else works. It reformats your hard drive and restores it to the condition it was in when you received it from Dell. There is actually a third way but that is a possibility only if you made a backup of the registry first.
You also asked whether you should contact Microsoft. I would say that you will get the same response from them that you did from Dell, that is that they won't troubleshoot it for free. The good thing is that you have the two Restore options to work with.
I think we all agree that the Registry needs to be fixed so the Windows System Restore seems to be the best option unless you get a better response on your e-mail to TuneUp Utilities, which I'm not sure that you will. When you run System Restore you will see a handful of restore points to choose from when you first run it. There is a checkbox to "Show restore points older than 5 days" and you should probably click that. Under the descriptions for the restore points most of them will probably say "System: Scheduled Checkpoint" if you have Windows Update set to automatic. You can look through the descriptions to see if one of them mentions a program installation but the tactic I would use would be to go back through one by one, do a restore and then test to see if the event viewer is working again. This way you don't make a bunch of changes to the system all at one time. You can pick a random one but it's hard to tell what will happen sometimes. However if you do a week or two of the System Restores and it doesn't fix it, you may end up having to do the Factory Image Restore. It isn't terrible (I did it quite a few times myself trying to troubleshoot a weird issue) but you have to make sure that all of your data (pictures, e-mail, documents, etc.) is backed up first and that can be a job trying to make sure that you don't miss something.
So, just to make sure that you are using the System Restore here are the steps. Click Start => Control Panel => System and Maintenance => Backup and Restore Center => then click on the link that starts with "Use System Restore..." => click Continue if the UAC box pops up and Next on the first page of the System Restore Wizard => there you will see the restore points, choose one, click Next and then follow the wizard until the end.
If you find that the System Restore doesn't work or you have any questions, let us know. I can get you started if you need to do the Factory Image Restore. Like I said I've had some practice using it. 