I have lost my pass for my laptop HELP!!!

Hello, there has been a personal problem lately. It involved the password to my laptop. You see my use is the Mast account on the laptop. I have an Acer Aspire 5315 and I tried to change the password the night before. However the entire time this little window kept popping up saying "Cannot change the password." So I gave up on it. Well later that night I shut down my computer without thinking about it. The next day I tried to log on and every pass I try nothing works. Not even the old one. I was wondering if there was a way for me to change it without having to go out and buy a floppy or USB?