Difference between DDR and SDR RAM..SATA & PATA HDD

[robins_mca]

Hi friends, can anyone help me to find out my RAM type? I am using a 256 Ram and I want to upgrade it by buying another 512 RAM. But I know it should be compatible with the older one.. How can I know the Bus speed and other details of the currently installed RAM..? And also what is the difference between DDR and SDR RAM..? What is the difference between SATA and PATA hard drives..? Currently I am using a SATA drive, can I attach another PATA drive and will it work smoothly..? Please advice me..

[Monty007]

What M/B do you have?