I do not remember the password to the main administrator account. I do not know how to install windows on this old pc. Anyone know how to uninstall windows then reinstall it? The bios can change the boot type, I have no extra drive to move stuff around with.
It's likely the Dell has a system image build intot he harddrive that you can use to restore the Windows as it was when it left the factory. If I remember right, back then you had to press and hold the CTRL key and press F11 when you power up the pc and see the DELL logo.
If windows has been upgraded to a newer version and you have no data that you need to recover then you will need your installation media. Boot from it, which may involve pressing an f-key when you start up the pc to select the boot drive, and when setup asks 'Where do you want to install Windows to?" you click the "Drive Options' link in the lower right. On the next screen you select and delete all the partitions and when the drive is empty you click the next button.
Again, the above assume you have no data you need to recover. If you do then you will need a device to recover the data to.