"Where can I get Dell Dimension cab files? I'm specifically looking for Dell Dimension 4500 cab files.
"

The driver cabs that are available today are all from the Latitude, OptiPlex, or Precision families. I don't think there are any plans to make driver cabs for the Dimension, Inspiron, or Vostro families.

I can see why the Dimension cab files not being released as the systems are older.

The Inspiron cab files would be nice though but I'm guessing since there are a lot more custom driver files (video cards) is the reason you aren't releasing them?

The focus of the driver cabs are the Enterprise class system familes (Latitiude, OptiPlex, Precision). This is why the consumer and small business class systems (Dimension, Inspiron, Studio, Vostro, etc.) do not have driver cabs.