Question : Problem: PC2700 DDR 333 MHz vs PC3200 DDR 400 mhz

Can these 2 types of memory be used in the same system.  What is the difference?

Answer : Problem: PC2700 DDR 333 MHz vs PC3200 DDR 400 mhz

If the computer will display the memory when using each memory module individually, it will more than likely run both, however I have seen instances where the PC would pick up BOTH if used individually, then get error beeps when installing both, OR, the PC does not beep, but just powers on and the monitor never wakes.  

Also, if you install both sticks and get 'beep codes' or the pc powers on but doesnt load, try reversing the memory modules in their slots, Module 1-into slot 2.. Module 2 into slot 1.  9 times out of 10 it will run both on newer machines.