We are currently using the latest version of ID3v2 for all our tagging as it is the most universally supported version of tagging for DJ software and hardware.
Unfortunately, other software and hardware titles such as Windows Media, Winamp, Windows Explorer, Vista, etc. use other tagging conventions.
Currently, iTunes is able to read ID3v2.4. If you import your tracks directly to iTunes after downloading them, you will see the ID3 information, even though it's not displayed when opening the files from a Windows program.
You can use iTunes to convert the tags back to an older ID3 version that could be read by my other software:
Just open the tracks in iTunes, right-click them, choose 'Convert ID3 tags' and choose an older version in the ID3 tag version dropdown list. Version 1.1 allows the tags to be read in Windows Media Player, Windows Explorer, iTunes and Serato.