Admin - but can't install programs

[akadcraft]

I have WindowsXP Home.

I am logged in with administrative privileges, but cannot
install Window Critical Updates (or any other software)--
get an error message that says I don't have administrative
rights. Even tried it in safe mode, using built-in
administrator. Still same error.

Can this be fixed without reinstalling OS? Will be too
much work to backup and reinstall everything.

 

[Guest]

I tried both admin and administrator- got invalid password

Tried leaving blank and when I hit enter I got the
C:\windows dos prompt. Tried chg dir to documents and
settings, etc and got and access to dir denied message.

thanks for the suggestions!