You can try a couple of things. The system file checker syntax in Windows 2000 is as follows: Click the Start Button, then Run. Then type in the Run Box "sfc /scannow" (without the quotes). This will check all the system files.
This file is also updated by downloading/installing the Microsoft patch for Media Player 6.4 and 7.0. Here's the website and the patch file download:
Patch for Media Player 6.4 and 7.0 that includes updated strmdll.dll file
And/Or, you can also do this...the file you're having problems with is a DirectX file, so you might want to to go Windows Update and download DirectX 8 for Windows 2000. This should overwrite the file in question. If it still shows up as corrupt after installing DirectX 8, I would suggest your problem lies elsewhere.