Presently I have ( 2 ) 512 MB Memory Sticks, DDR, 2100 in my Desk top computer, need to up grade the memory, will DDR2 or 3400 DDR sticks work on my computer or should I stay with just DDR ??
Unless your motherboard supports both DDR and DDR2, you'll have to get DDR memory. What system or motherboard do you have? If you don't know, then CPU-Z might be helpful.