WinXP: No Administrator's Privileges

[Trdi]

I am the only user on my PC (no guests allowed) and on some occasions it seems I don't have all admin privileges. For instance I can't manually start some of the services (Windows installer, Print Spooler,...) as I get "Error 5: Access denied". I've got one problem which won't install without the Print Spooler started. It cleary says, that I don't have the Administrator's privileges. I've been receiving occasional messages from many programs about me not having the admin rights for almost a year. What's the problem? What should I try to solve it? Thank you.

[vidster]

And have you tried booting in to safe mode, then access the Admin account from there Trdi?.
If you are the only user, you should have no problem

BOOT IN TO SAFE MODE: Press f8 repeatedly while rebooting. When the boot menu pops up, select safe mode.