Computer Owner Don't Think Ultimate Admin Yet

I purchased my HP from a big computer store with Vista home installed on it. It was an out of the box sale (I thought I could avoid a wait for the comptuer I wanted). The company that sold it to me was listed as the administrator. The old owner took off their password before I took possession of the computer I purchased. I followed instructions on how to put on a password to start the computer. However, there are dozens of fiels named after the previous administrator. I tried to find out how to change the administrator globally to my name. There is still an administrator account name and it appears the previous administrator is still above my permission status - even though i am the computer owner, don't think I am the ultimate administrator yet. I read that not being able to use screen print was a result of not being the administrator. I can't make the screen print work either. I assume some members have dealt with these matters before. I directing me to some good "how to fix" information.