Ok I suggest you boot into Safe Mode by selecting F8 during the boot sequence. You have to be quick as you only get about 2 seconds to select F8 or it goes into the normal boot sequence. Select Safe Mode from the list of available options and eventually at the Logon screen you will see another account called Administrator. This will also require a password but I suspect it will be blank i.e no password. When you are logged on go to Start/Control Panel/User Accounts and set up a new user for yourself with administrator rights.