There usually is a way to reset bios passwords, but this information is usually available only in technical repair/maintenance manuals which might or might not be available on the Net. If you have some kind of a service contract just ask the technical support for advice.
The other possibility (I think I’ve run into this with some older Thinkpads) is that the firmware thinks the configuration has changed (caused by a flaky contact or some interference) and the change needs to be confirmed in BIOS. In this case one would assume that the default password would work…
Third possibility that comes to my mind is that some program has changed the BIOS settings (I assume this laptop has modern flash bios where this would be possible). It might be some malware or it might be someone who did something that s/he did not understand.
Edit: After a little searching, it seems that there is a “Compaq Presario V2600 Notebook PC – Maintenance and Service Guide” available in which there are instructions how to remove the RTC battery. Removing that might cause the CMOS to reset to it’s defaults and thus get you rid of the password. Then again it might not, I’ve never done this to any Compaq product.
Removing the battery won’t do it, get a master bios password at bios-unlock.com that 10 digit code is the key.