Originally Posted by Atomic Rooster
To answer your question, yes. Your DDR2 667 will work just fine on that motherboard.
If you do buy another 2GB of DDR2 800 to install along with the current memory, it will run at the same speed as the DDR2 667.
i have ran different speed RAM together and read this to but when you use 2 different speeds of RAM together the system isnt as stable it will work but if the timings on the higher frequency RAM is faster than the lower frequency RAM there would be major stability issues when i did mine i got constant blue screens took out the faster RAM and it was fine. so be aware of this.