I was working on my buddies COMPUTER, after he has been having troubles with it for a while now, especially online.  Its a Compaq with Vista on it.  First thing I did was take it all apart and thoroughly CLEAN the case out and all the innards and then put it back together.  I then started it up and began to go through everything checking for problems.  I eventually ran an error scan on the hard drive and let that run through.  It came up with a TON of errors and even after letting it sit and scan for well over 24 hours, it was not scanning very much anymore.  Within a 12 hour period, the message on the screen only added one thing and i believe it said something like: trying to fix error in sector .... then the next message was the same thing.  Like it tried to fix, but failed and was trying again.  I got fed up of waiting so long, so I hard restarted the computer and basically had to revert the computer back to factory settings, which wiped all of his information.  Now here is where it gets CONFUSING.  I have recently graduated from COLLEGE with my Associates in I.T., so I kind of know my way around computers, but I have never even heard of this before.  Whenever I have encountered HDD's that have bad sectors on them, they have all been junk and had to get tossed.  After the computer restored to factory settings, I did the test again, but this time the HDD came out perfectly clean.  Not a bad sector on it.  Absolutely nothing wrong with it at all.  I have proceeded to get the computer back up to date, and I am basically ready to give it back to him, but I needed to find out if anyone else has ever had something like this happen?  Is it possible it was a virus or worm or something that was messing with the hard drive.  Like I said, I have never heard of that happening, and as far as I have ever known, if it was a worm, then wouldn't the HDD be shot?  Either way, I will make the suggestion to get another HDD installed for backup, in case this one decides to take a dump again.Can you post the hard drive report next time for checking? Is it a windows checkdisk startup or a software diagnostic test? The bad sectors are blocked off when found....that's why they aren't showing now...Hi there

This is quite rare and sometimes happens when different software is used for the scans. I see that the situation here is different.
From my experience, I think it is a good idea to check the drive with the manufacturer's software. You are fortunate that the drive seems OK now, but I would not rely much on it. Backup drive or scheduled backups on an external may be a nice advice.

Hope this helpsWelcome Aboard R2....

Good to have a Rep around.Thanks!Hi

Sad that you didn't make the first thing you did a full backup of the hard drive, which could have saved your friends data.

Before you give the computer back it would pay to do some more diagnostics on that drive. It maybe that is thermal and is failing when warm. A program that is really good is MHDD from here http://hddguru.com/software/2005.10.02-MHDD/

I polity suggest   you get a copy of Minitool Disk manger (it's free) and use the boot cd to backup hard drives before reloading windows. If this isn't possible because of to many bad sectors or a failing hard drive at least use the file manager built in to copy off what is important. Doing a windows reload and losing someones data is what gets the computer industry a bad name.