To open the tray try holding Mouse button down while starting, also, you can open the door at the top, look for a tiny hole to stick a straightened out paper clip in to open the tray manually.
If 10.5 be sure not to use a 10.4 or less Install Disc to repair the drive.
Could be many things, we should start with this...
"Try Disk Utility
1. Insert the Mac OS X Install disc, then restart the computer while holding the C key.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu at top of the screen. (In Mac OS X 10.4 or later, you must select your language first.)
*Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.*
3. Click the First Aid tab.
4. Select your Mac OS X volume.
5. Click Repair Disk, (not Repair Permissions). Disk Utility checks and repairs the disk."
Then try a Safe Boot, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, reboot when it completes.
(Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive.)
If perchance you can't find your install Disc, at least try it from the Safe Boot part onward.
Tough without the Install disc, but some things to try...
Does it boot to Single User Mode, CMD+s keys at bootup, if so try...
Repeat until it shows no errors fixed.
(Space between fsck AND -fy important).
Resolve startup issues and perform disk maintenance with Disk Utility and fsck...
Does holding alt key at bootup show any boot options?
BDAqua, Thanks for the suggestions. I was able to get my disc drive open so I could insert the Apple Hardware Test disc (note, my disc is for OS 10.3, but I have OS 10.5.4). When I followed your reboot commands all I got was a black screen instead of a white screen. I waited for several minutes to see if the black screen would clear so I could run the diagnostics, but after several minutes it remained a black screen.
Later I tried the safe boot (Shift-S) and single-user boot (Command-S), but still got the blank white screen. I tried holding down the alt key at boot-up and just got a dark, black screen (no light in the brackground).
I will try these solutions again later when I have more time, just to see if I get any different results. But for now I haven't seen anything other than blank screens. I do get the boot-up sound when I first turn the computer on, but nothing happens after I get the screen.
Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...
Do you have another Mac around with Firewire, & does this one boot in Target mode...
A startup chime is a good sign. If you have no video, try resetting the PRAM.
If still no go, can you attach the monitor to the MacBook Pro, to test that the screen works. Also try and determine if the cable is good.