[help] SQL Error - I/O Error 2 (The system cannot find the file specified)

Windows 2000 Server SP4 + SQL Server 2000 Enterprise Editon SP3,RAID5.

the windows event log give the following error information:

I/O error 2(The system cannot find the file specified) detected during write at offset 0x0000010c6c4000 in file 'D:\Program Files\Microsoft SQL Server\MSSQL\data\GJSZBANK_Data.MDF'.

I have searched microsoft knowledge base and got this article:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;828339

but don't understand some contents in the topic:

For example, if you encounter the following error message in the SQL Server Errorlog file, SQL Server encountered operating system error 2 when it uses a Windows API call to write to the tempdb primary database file:

Error: 823, Severity: 24, State: 4
I/O error 2(The system cannot find the file specified.) detected during write at offset 0x00000000284000 in file 'D:\Program Files\Microsoft SQL Server\MSSQL\data\tempdb.mdf'

Because SQL Server has already successfully opened the file and did not receive an Invalid Handle error, the error is likely being raised in a lower-level kernel software component, such as the file system or a device driver. This problem does not indicate a problem in SQL Server, and it must be investigated as an issue with the file system or a device driver that is associated with the file.

Does that mean this is not a SQL Server error?
Does that mean something wrong with my operating system? or something wrong with my hard disk?Are there any errors in the SQL errorlog? Or is it only in the NT Event log?