Yes , you can add RAM up to 1 Gig or 512 X 2.

The ram must be installed in pairs:

If you want ;

256 = 128 X 2
512 = 256 X 2
1024 ( 1 Gig ) 512 X 2

Very easy to install , but , must be PC100 or PC133 /168 pin Dimm`s

Best of luck to you,

Gary 