If this a BIOS password you need to call Dell Technical Support, verify your ownership and pay for the support. Its not worth it for such an obsolete model.
If its a Windows password, you'll need to manually clean install Windows. Windows XP has reached end of life and its not recommended you continue using it. The hardware of the system is pretty poor so its not worthwhile upgrading it to Windows 7 32 Bit and the video will likely be incompatible with Windows 8.1 32 Bit or Windows 10 32 Bit.
For BIOS Admin password, there are password generation programs available on the web to get you back into your BIOS and unlock it. This old Inspiron 6000 should display a #<service tag>-595B code on screen and all -595B laptops can easily be unlocked.
I confirm the previous statement: performance under Win7 is kind of poor on the Inspiron 6000 and GMA915 graphics not fully supported (no Win7 drivers means requirement to install XP ones). This is a very old laptop that has long reached obsolescence.