If you're on XP, off Control Panel, choose"Power Options". Click on the "Advanced" tab, and uncheck the "Prompt for password when computer resumes from standby" box.
Or, if it's a BIOS password, there is a way to clear it, also. Let us know if you have (for sure) XP, if it's really a BIOS password, you're trying to disable--it's one that is required before Windows even loads.