CavVet, I had this problem before on an original PS2. Try putting in an older PS1 game, or music CD. If it loads the CD's then you need to adjust the potentiometer on the DVD side of the laser, if it reads neither, then both the CD side and DVD side pots need adjustment. Normally when this happens you get a disc read error.
I paid some guy on the web $8 for a digital repair manual that showed this procedure and other common PS2 issues and fixes in detail.
I will try to find it for you if this is your problem, it covers everything from opening the case to removing the parts to get to the laser. It was very comprehensive.
ETA:
I also had a problem like this that was from dirt, dirt that I couldn't even see on the disc. I used the Skip Dr. DVD cleaner and the game loaded.
Another time I had a bad memory card, see if you can get into the memory card by itself to elimiate this as a problem.