error event id 12294 source sam

i'm having this error event id every on and then on microsoft 2000 enterprise server with exchange, every time event id 12294 appear there will be lots of error evet id 2019 following it, would like to know how to get rid of it.

Event Type:      Error
Event Source:      SAM
Event Category:      None
Event ID:      12294
Date:            11-09-08
Time:            8:02:55 PM
User:            MOCSB\Administrator
Computer:      PDC-MY
Description:
The SAM database was unable to lockout the account of ? due to a resource error, such as a hard disk write failure (the specific error code is in the error data) . Accounts are locked after a certain number of bad passwords are provided so please consider resetting the password of the account mentioned above.

Event Type:      Error
Event Source:      Srv
Event Category:      None
Event ID:      2019
Date:            16-09-08
Time:            7:00:33 AM
User:            N/A
Computer:      PDC-MY
Description:
The server was unable to allocate from the system nonpaged pool because the pool was empty.