|Laptops are frequently stolen.|
Whther it was you who stole it, or if you unknowingly bought a stolen computer, or whatever, we have no way of knowing whether you have a legitmate right to access this computer's present user installation.
When a laptop has been stolen that has a password, or if someone buys a used laptop not knowing it was stolen and discovers it has a password, it is very common for whoever to claim in a post on the web that the former user claims he or she has forgotten the password. It is extremely unlikely that if they were the legitimate owner and had to use the password every time they used the computer that they would forget it, even if they have not used it in a while.
Even if they did forget the password, in some cases, if they contacted the manufacturer and have sufficient proof that they are the legitimate owner, then the manufacturer will supply some info that will remove the password, or a technician that is certified to work on your brand of computer will be allowed to do that for you. Often the manufacturer will only do that for the original owner.
If it is only the operating system that has the password, then running the proper Recovery procedure for the model as OtheHill has suggested will re-load the original software and allow you to use the computer - the original user's data will be gone - there's no need to be concerned about whether you should have the right to access the former user's data.
If you didn't get the proper Recovery disk or disks with the computer, if the laptop is not more than about 5 years old, you may be able to order the proper disk set from the Dell site.
If you can't get that set anymore, OR in any case, you can search for the Recovery disks on the web for your specific model - there are a small number of web sites that have those - they're either copies of the original disks if they came with the computer, or they're copies of a Recovery Disk set made in Windows by using a brand name supplied program to do that by someone who had the model of computer.
If your laptop computer is a Dell model newer than about 8 years, or a HP or Compaq model newer than about 5 years, I know from experience the hard drive probably does not have a Recovery partition that can be used with a single Recovery CD to restore the contents of C, at least, the Compaq and HP models I worked on don't. The HP and Compaq models have a hidden second partition but it's used for something else. All of them - Dell, HP, and Compaq models - came with one or more disks when new - if it had XP Home or Pro on it, the disk or one of the disks is a slightly modified regular OEM Windows CD. E.g. a Dell I am working on has that - "Reinstallation CD" "Microsoft Windows XP Home Edition". The HP model I worked on also came with a DVD "Drivers and Applications DVD" that you use to install the needed drivers for the system and the HP supplied additional software. I assume it's the same or similar case for Compaq models. The HP model also came with a CD to install the software feature on the second partition. That doesn't come with the HP supplied Recovery disk set when you order it from the HP site (I ordered it, then found her original disks later). I assume it's the same or similar case for Compaq models.
However, if the password is for accessing the hard drive, for laptops newer than about ten years old, that's built into the mboard, the password and whether or not the access to it is enabled is stored on both a chip on the mboard, not the bios chip, that cannot be erased by removing all power to it, and on the hard drive in a location not accessible by using any normal software. Programs you can get on the web that can remove passwords on older mboards won't work with these more recent laptop mboards. Very few people know how to remove that info from the hard drive - most techs simply replace the hard drive. The chip the password info is stored on must be removed (un-soldered) from the mboard by an expert and replaced with one that is already programmed, or you have to replace the mboard with a new or used one that does not have a password.
The info in response1 is only of use if you can't log on to a specific user in the operating system but the Adminstrator has no password. In that case, at least in 2000 and XP Home, Pro, and MCE, you can boot into Safe mode, log into the Administrator user, Delete the user you can't access, which will delete all of the user's info in C:\Documentsand Settings\(that user) \all sub folders and the (that user) folder, then when you boot normally, you can create your own user.