1536 max total memory is supported. The empty slot (after removal of the factory 512 that must be pulled first) can't take more than a 1gb stick (which is a pity). Needs to be PC5300 (533mhz) DDR2. The other factory 512 is soldered to the board (pity #2). Hope the soldered on stuff never goes bad! With dilusions of grandure I too tried to push the envelope and stuffed a 2gb stick in the expansion slot...same result...eternal blank screen. Even still, the extra half gig was an appreciable improvement because 192mb is being sucked away right off the top by the video. At least now the system has a good 1.3gb fully available after the video overhead. Throw in a 2gb SD or MicroSD also and dedicate it to SpeedBoost (im running Win7). This helps even more. Machine's quick enough at this point that I don't have any complaint. Runs Win 7 great even though it claims to be unsupported by this little machine.