The 1st thing you have to do is try to determine if it’s merely a software issue with your OS install or if the problem relies on the hardware (whether it’s the screen or the computer itself).
In order to facilitate that task, you must check the obvious.
1) The DVI adapter (already tested).
2) The Screen. Can you hook the monitor to another computer?
3) Can you hook another monitor to the same computer?
Extras: Have you tried another VGA cable?
The above should result in any of the following:
a) The screen is defective, change screen.
b) The Mac mini has a hardware issue where no other screen works. Time for repairs (probably not worth).
c) The Cable is defective, change cable.
d) The screen works fine on another computer, the Mac mini works fine with another display. what…?
In case of D, there could be a problem with the software instead, either the driver that the Mac mini is using when it detects the display is broken or the video driver or something. That’s a whole new world and -as already suggested- you might want to try booting from the install CD/DVD and trying to see if video works there. Back up your drive and a full reinstall might also help you have everything fresh.
Hope it helps. I know it’s a lot of obvious steps, but this is how the tech guys do it :) Find the problem first.
UPDATE:
After reading that the Mac mini doesn’t work with a different screen and that this issue happens before login screen (i.e. it’s not ‘user’ related), there are two possible ideas you can try before a complete OS reinstall.
You mention that it works in Single User but not safe mode; given that Single User goes straight to the command line, have you tried running fsck on the partition? Maybe there’s some data corruption in the OS X volume.
Safe Mode doesn’t load external drivers and items in the StartupFolders, so that should work and I find it weird that it doesn’t. Of course make sure you unplug all external devices (sans keyboard/mouse/display) before diagnosing a problem like this.
In any case, I’d try to install a fresh copy of OS X on an external drive (if you don’t want to wipe your internal copy) and see what happens from there. If the external copy works, then the OS X copy has a big problem. I know this is obvious (and it’s already in your list of things to do) but sadly debugging a problem like this without access to the OS/hardware is really hard. You can always later clone the freshly installed OS X to your internal drive to avoid the reinstall in the internal drive.
Good Luck!
You might try attaching the second monitor and running Apple Hardware Test upon boot.
To run the hardware test:
- Print these instructions for reference
- Disconnect all external devices except the keyboard, mouse, display, and speakers. If you have an Ethernet cable or external DVD drive, disconnect it.
- Restart your Mac, holding down the D key while the Mac restarts.
After your Mac restarts, you should see the Apple Hardware Test chooser screen. If you don’t, Apple Hardware Test may not be available on your Mac. You may be able to start Apple Hardware Test from the Internet. Reconnect your Mac to the network, then restart your Mac while holding down both the Option and D keys.
When the Apple Hardware Test chooser screen appears, select the language you want to use, then press the Return key or click the right arrow button.
- When the Apple Hardware Test main screen appears (after about 45 seconds), follow the onscreen instructions.
If you can't see anything on your secondary display after starting Apple Hardware Test, then it may have started but not recognized your secondary display. You could press Enter and then T to start the tests, but there's probably no way to see the results. If this is the case, you're probably better off taking it to the Apple Store. It sounds like the LCD is faulty.
Here is a list of other startup keyboard shortcuts.
LCDTest
You might try running this LCDTest program to check whether any RBG test patterns show up or change the display output. If you still don't see any output, and you've checked that the LCD Display shows up under System Preferences => Displays, then you may have a hardware problem with your Display Data Connector, or LCD Display.
LCD Hardware Problem
This is most likely a hardware problem, and taking it in to the Apple Store for support is probably your best bet if it's still under warranty. You can check if your Macbook's warranty is still active by visiting this page and entering your serial number.
If it's out of warranty, or you really want to try and solve this yourself (this will void your warranty), then dive into the iFixIt Guide for Replacing a MacBook Pro 13" Mid 2009 Display. iFixIt sells Replacement Parts for your Macbook.
Best Answer
This turned out to be the DVI-cable. For some reason, the DVI-cable works better with my PC than the Mac. I plugged it in via VGA and it works.