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.

CAUSE

When you install Windows Media Player 7, it does not update the Cdr4vsd.sys driver."