ABS Light

I have a 1994 Chevrolet Cavalier 2.2L Automatic. I have had a small problem lately with the ABS Light. It comes on whenever I drive, however, there is no real consistancy. It never comes on when I hit the brakes, but comes on only when moving forward. Sometimes it happens immediatly while other times it happens a while down the road. My brakes work fine, but I do need to clear this ABS problem.

I tried unplugging the battery for about an hour and a half and it didn't work. I also tried using a test light to see if a sensor was sending a signal, but nothing was coming up.

I was thinking about getting a diagnostic tool for my laptop to use on my computer, but I am not sure what to get. First I was looking online to see if I could find out whether or not I have an OBD I or OBD II port. Next, I would like to get a quality tool so I can use it for other vehicles as well.

Thank you in advance for your help.