580MT Upgrade to SSD HDD Combo

I tried to insert a link to the spec for my Inspiron 580 MT : Intel Core i5 Processor 750(2.66GHz,8MB)  but this forum interface defeated me.

I have two questions:

1. Why is the RAM shown as limited to 8MB?  Elsewhere, inculding some answers on the dell community forum imply that it is possible to install 16MB (4x4MB).  Some report having done this successfully including confirmation that the memories are working correctly post installation.
   
   
2. The spec also shows that the hard disk drive is limited to 1.5TB.  Why is this?  As I understand it, the processor is capable of 64 bit operation?
   
   Thank you