Administrator missing

OK, hopefully somebody out there can help on this one, as I have not seen
anything like it among previously asked questions.
My laptop, which was purchased about a year ago, came with Windows Vista
Home Premium installed. I set up my single account as an adminstrator and
everything went fine for a long time. A couple of weeks ago, however, I
realized that I never had my parents set up parental controls for me. So I
went onto user accounts, created an adminstrator account for my mother, she
put in a password, switched my account to standard, and then set my controls.
Since then she has not been on my computer to do anything, but today I needed
her administrator permission for a download. But when she typed in her
password, it said it was incorrect. She is certain that it was the right one,
and we even tried different variations to account for a possible error in the
original entry.
The obvious solution to this problem would be to reset the password. But
when I went to "switch users" the log-in screen came up with only my
username, and no option to switch. This is probably not a new thing, as we
had never even attempted to log onto hers before, so I would have never
noticed the lack of options on the log-in screen.
So the basic problem is this: I am not approved to download, and I will
probably run into other important processes for which I also am not approved.
The adminstrator account cannot be accessed, and I am pretty stumped.
Any help or suggestions would be greatly appreciated.