Two days ago I was doing a defrag on my hard disk, but a power failure screwed the process. After the power failure the computer won't boot. It says something like: "Error, hal.dll is missing or corrupted". After that I went like crazy because the documents there are really important to me, so I tryed many things: boot in safe mode, overwriting that file... but none of them worked.

After that, I reintalled the OS and I have tryed to retrieve my documents from the previous installation but when I try to access the "My Documents" folder, it says: "Unable to access folder. Access Denied". Can somebody help me retrieve that information please?

Did you do a complete new install (including a reformat of the partition)? If so, it will be difficult to recover much of the data. I assume that your data is still available because you get the Access Denied error.

To solve the Access Denied problem, there is an article on Microsoft's website about this.

Tip for next time (not that I hope it will happen to you again ;) ), there is an easy fix to your hal.dll error which probably would have saved you a lot of trouble.

I don't think Windows (any version) let's you re-install without formatting the current partition you want it on so I think you just might be screwed as far as your data goes. Sorry to hear that.