Can't open system preferences...

What happens if you select it from the Apple menu in the menu bar?

 

Repair Permissions:
Open Disk Utility (/Applications/Utilities/).
Select your Mac OS X startup volume in the column on the left of the Disk Utility window.
Then click the First Aid tab. Click the Repair Disk Permissions button.

 

can't open system preferences

i can't open system preferences and delete files from anywhere, I've tried to repair permissions and delete files from terminal but now i can't do it, it says "command not found" please help me i looked everywhere on the web and nothing seems to work. Thank you

 

What files did you delete, and what command is not found?

 

Yeah, basic troubleshooting can solve a LOT of issues, depending on how serious the problem actually is. There have been more than a few posts on here about problems that simple permission repair/reboot fixed.

Others required a reset of the PRAM, and some more serious ones require more.

I made a post to outline the basics of it, Here

 

i have some files on desktop the only way i could remove some was by the terminal (mr -f (name of file), i can open most my files but not delete them, i can't access messenger and system preferences. i ran fsck and pram but did not solved the problem, everything else is working fine. this happened when i installed lexmark software on my mac.
thank you

 

are the files locked for some reason? Did you repair permissions?

 

There's only one item I can think of that you can try and that's logging in as ROOT, removing Administrator from your Account, giving yourself Administrator permissions again, and then never using ROOT again. Here's a way you can try to get into the user ROOT.

1. Start the computer up in Single User-Mode: When turning on the computer press and hold Command+S till it takes you to the black screen with white text.

2. It tells you, to start the computer type in these commands... type in the one that says mount -rw / or something like that.

3a. Now I'm not sure if you can do this here or not, but type in: passwd
And set the password you'd like to use.

3b. If 3a didn't work, type in the command (it shows you above) sh /etc/....
While this is loading up keep typing in passwd, till it asks you for the password (it takes some timing, and you wanna keep the password short, simple, and easy. I've done this one on an iBook G4 and 2 PowerMac G5s. It can be done.

4. Instead of logging in as your user, log into root (username: root password: whatever you typed in in 3a or 3b).

5. Open System Preferences and try to change your user permissions.

Try that, and post your results.