Supports 4 Gig Max but 3 gig with 32 bit OS.
Memory Type: DDR PC2700, DDR PC3200, DDR (non-ECC)
Maximum Memory: 4GB
Each memory slot can hold DDR PC2700, DDR PC3200 with a maximum of 1GB per slot.*
Although the memory can be installed one module at a time, the best performance comes from using matched pairs of modules.If your model uses the Pentium 4 with a 800MHz Front Side Bus (FSB) you must use the PC3200 parts. If your system has the Pentium 4 with the 533MHz Front Side Bus (FSB) you can use either the PC2700 or PC3200 parts.
How much memory your Windows OS will recognize depends on which version of Windows you are running. 32-bit versions of Windows will see (and utilize) only 3GB or 3.5GB. To utilize more memory, install a 64-bit version of your OS. More information about OS memory maximums can be found here.