See Knowledge Base article Q269381.
"After you install Windows Media Player 7 on a Microsoft Windows 2000-based computer, you may experience any of the following symptoms:
The computer stops responding (hangs) during startup.
Your CD-R/CD-RW drive is not recognized when you use Adaptec Easy CD Creator or DirectCD.
You receive a "Stop" error message at startup.
When you install Windows Media Player 7, it does not update the Cdr4vsd.sys driver."