I've had success in forcing entry to a password-protected CMOS by simply making some change in the configuration. The most radical, but the most certain course of action is to wipe out all CMOS settings. This will immediately set the CMOS to system defaults. Here it will be necessary to wait from 10 minutes up to several hours for an equivalent result. Very often, especially with PS2s and laptops, the battery must be removed and then replaced.
Several hours is very likely.
On older motherboards, you'll have to manually enter the figures. Open the case and look. If this is not so, then contact tech support for your drive. They all have automated info and fax back lines for this. Laptops can be handled in the same way.