windows cannot access specified path, may not have permission

the following is a list of the symtoms
- I can't access virtually all exe files & all desktop items. I can open the shortcut or folder eg my computer, but it won't allow me to do anything in there
- I can't access control panels or start any new programs.
- It won't let me switch off the machine
-I tried rebooting in safe mode, but it was unable to do it.

I don't know what to do! I would like to try uninstalling comodo to see if that is the problem, but i can't in add/remove programs, and i dont know how else to do it.

I read that some people reinstalled windows, but i don't know how to go about that either. mine came with the computer, so i do not have a disk.

When attempting safe mode, there was an option of reconfiguring computer from last ...something... but i have no idea what that would do... would i lose all my pictures, etc?

if anyone has a solution, i need step by step instructions, lol.

oh- running windows xp