I have 2 512 cards installed and the computer only shows that I have only 512 installed and it should be 1 gig?? What would be the cause of this?

There could be many reasons,
1 Either the RAM slot is not working
2 or the RAM card(s) are not OK
3 or the RAMs are not compatable(not of the same specs)

Solution
1 Remove both the RAM cards, clean the metal joints in both the RAMs and the RAM slots
2 Remove power, remove all power source, remove power cables including all the battery
3 Keep presssing the power switch ON for a few mins, Do....ON... OFF, ON... OFF WITHOUT any POWER
4 Replace battery, power adaptor, power cables etc
5 Insert one of the RAMs in 1st RAM slot, power on, check if it's OK, Switch OFF, remove the RAM
6 Do the above process for the other RAM, now check if that works, use the same RAM slot
7 Now do the above two steps for the 2nd RAM slot

It will give you a rough idea of where is the issue.....either RAMs are not OK or the slots have issues or there is a compatibility issue among the RAM cards.....

Pls reply back and leave a feedback
Regards
Kris