Music will not add to iTunes (MP3 Format)

Question

I'll try to make this quick. About a month ago my hard drive was over flooded with MP3's. I decided to get an external 250GB Hard drive. I moved all of my files over to the external hard drive. iTunes "lost" the connection to those files. Rather than re-define the location of my files inside of iTunes, I took this opportunity to re-organize all of my music.
1. I uninstalled iTunes
2. Deleted the iTunes directory under My Documents\My Music\iTunes
3. Re-installed the latest version of iTunes.
4. Reactivated using my AppleID
I won't even get into how upset I am that the music I purchased is no longer available to me. I find it nearly insane that I can see a list of the music/games I PAID FOR but cannot re-download them. Therefore I've lost those songs and the Suduko game I bought. Lovely.
This is where the problem starts. I do a FILE <-- ADD FOLDER TO LIBRARY and then I select the folder to add. Some folders add with no problems while other folders will not add. Here are the steps I have taken to resolve the problem.
1. Try to drag and drop the songs into iTunes.
2. Try to do a FILE <-- ADD FILE TO LIBRARY (1 file at a time)
3. Moved songs back to the C:\ drive from the external drive.
4. Rename the music files.
5. Using MusicBrainz Picard, I re-tagged (ID3) the files.
6. Uninstalled iTunes and installed an older version (v.7.0)
7. Sent a music file to my friend (here is where it get's interesting)
Now, my friend ALSO cannot add ANY MP3 file that I send him, but he can go out and download the exact same file from the internet and he can add that file with no problem. What does this mean? Is my computer corrupting my MP3 files? Some things to note:
1. I've used Windows XP SP2 to edit my ID3 tags by using the Right-Click <-- Properties <-- Summary Tab to fix or correct some of the names of the artists/albums. Could I be causing some ID3 tag problems when I use MusicBrainz or Windows XP SP2 to change my files?
2. When I try to play one of these "bad" MP3's in iTunes, it won't play the song but when I attempt to play the song using Media Player, I have no problem listening to it.
Any ideas? I'm frustrated and lost. It's been a month without my music on my iPod and I'm wondering if their are any other programs aside from iTunes that I can use with my iPod.

Answer 1

Update - The problem is within iTunes. This is an educated guess but when other applications have NO problem playing, and reading (ID3 Tags) of the same MP3 files that iTunes CANNOT see, this must be an iTunes problem. These are the programs that can play and read ID3 tags on my MP3's:
1. Windows Media Player
2. WinAmp
3. Songbird
4. VLC Media Player
5. MusicBrainz
Also, I used a freeware app named ID3 cleaner to do a test on my MP3's. The program scans for corrupted ID3 tags on MP3 files. It found no corruption on my files at all. I have also converted the ID3 tags on my MP3's to older version thinking that iTunes might have a problem with ID3 V2.4. I took it back to 2.1 and this didn't solve the problem. I'm very frustrated with iTunes and will be using SongBird to work with my iPod for now on. I'll just cut my losses as far as the $50 I've spent in the iTunes Store. If anyone has any other recommendations to fix the problem, I'd love to hear them.
I know I'm not the first person who can't add/import MP3 files into their iTunes library. Doing a search in Google shows hundreds of thousands of hits. At this point it's a complete mystery to me. Something in some of my MP3 files makes iTunes unhappy. This was NOT a problem about 4 months ago. I have a feeling that the most recent releases of iTunes (since the iPhone) has some major bugs. I've been an iTunes user for only about a year but in the last 4 months I've had more problems with Quicktime / iTunes than I have had in the other 8 months combined.
Thanks for reading my unneccesarily long rant I'll check back, seems like a lot of good and helpful people come into these forums. Must be the Apple state of mind
-D