This is a very, very simple and legal (I supposed) way to install Windows Media Player 11 without validating.
The only tool you need is WinRAR. You can get it here.
- Extract everything using WinRAR from wmp11-windowsxp-x86-enu.exe
- Install wmp11.exe then restart Windows.
- Install umdf.exe, wmdbexport.exe and wmfdist11.exe then restart Windows.
- Now extract everything from wmp11.exe.
- Go to update folder and run update.exe.