The fix varies with what version windows. Skill helps a little here but mostly on the pocketbook.
For example I use NTPASSWD (see google) which is free but some folk can't make or boot the CD which means they have to use something like http://www.lostpassword.com
At least it's cheap enough.
Please keep in that I'm more of a newbie than anything else. I own my computer & thought I was the Administrator but when I go into Task Mgr. It asked for my password which I don't know. A few years ago a friend of a friend came and cleaned the computer or something & used "test" as the owner. How do I find my password?