With stories of years and thousands of iTunes music libraries being lost, many are rightly reluctant to clean up their slow Windows PCs.
I managed to do so, and you can too. But it got tricky. It's not as straight-forward as it could be. But if you follow the Tips here, you'll be fine.
Firstly backup all your M4A and even MP3 files onto a USB hard disk drive.
The easiest way to do that is to get Windows to do a search on *.m4a then RIGHT click on an item found. Then press Ctrl+A. Next RIGHT click on an item and and click on Copy. Lastly go to your USB drive and also RIGHT click on a blank space, then click on Paste.
When copying is done ensure - double check and triple check - that the number of tracks on your USB drive matches the number of tracks in your iTunes library!
Once you are sure you have everything backed up you can erase Windows and install a fresh new copy free of bloatware or malware. (Also check out our other Tips page on how to keep it that way.)
On your new PC launch iTunes (easiest is to install it from http://ninite.com) and go to Edit/Preferences/Advanced. When there ensure "copy to iTunes music folder when adding to library" is checked.
Then go back to the main screen of iTunes and in File/Add File To Library, select the folder on your USB drive and click on one of the songs. Then press Ctrl+A to Select All. Next press Enter on your keyboard.
The tracks will start being copied onto iTunes and placed into folders by artist and album automatically.