good day mam/sir..4 days ago, i bought 2GB elixir ddr2-800 (PC2-6300 400mhz) to upgrade my emachines d725, currently with 2GB DDR2 (PC2-5300 333mhz)..i install it with my 32bit win7 OS right now..and it says that only 2.92GB are useable..therefore i install 64bit win7 OS..after successfully installing it and setting up some options like usernames etc..after that the system reboots then a black screen with blinking ' _ ' at the upper left..seems that it cant boot up to windows 7 logo.... what am i mistaken?does my emachines d725 t4300 not compatible with 64bit win7 ultimate?or its the ram issue?pls. reply as soon as you read this (at your convenience)..i wanted to settle it down today..i have a lot of work to do ...please? thanks in advance everyone. -reymelito p.s. -->i already removed the new 2gb ram (ddr800 pc2 6300 400mhz) and retain the old 2gb ram but nothing happens.. ..