Whether I try to update Acrobat from within the application or from the Adobe web site's download, neither the product nor security updates will install.

From within, the error messages are non-descript, only that there was a problem. When trying to run the .MSP downloaded file, the error says that "The installation source for this product is not available..."

I am running Windows XP Pro 2002 SP2

It sounds as though you need your installation disk.
When you installed Acrobat, did you do a "complete" install?

Try repairing Acrobat and then install the updates.

J.R.