hello, your motherboard uses DDR2 and can support up to 4 GB
if you want to add more memory, it is necessary that the frequency (eg 533MHz) is the same on all the memory chips. for example: two strips in 2GB 533Mhz.
nevertheless beware, if you are in XP, the transition in Seven will not necessarily possible. (Sorry for my English because I am French and my level of English is bad).
I remain at your service to further questions