run crucial ram scan:
http://www.crucial.com/systemscanner/index.aspx
see list of compatible ram/max ram
compare compatible ram with ram you purchased already
google to see if machine is compatible with ram increase good keywords include 'your pc model number' 'maximum ram'
in your case the E Machines T3120 has a
Max Supported RAM 2 GB
all good so far? continue
go into system bios (when ur PC loads up you press a key (del/ins/f2/etc) to open up bios menu. Bios menu is very dangerous to edit if you don't know what your doing. Check what the bios detected as your current ram. You might be able to again verify the current ram you have here + mb you have here. YOU ARE NOT HERE TO EDIT ANYTHING JUST GATHer INFORMATION ABOUT RAM. It is recommended you do not save changes on exit.
purchase compatible ram with information you have gathered; remember going cheaper increases the likelyhood that you will get faulty ram; of course most sellers will replace faulty ram, but think of the hassle and time wasted
install ram in your PC and ensure you have secured the ram into its slot. It is critical to remove any power source on your pc. Ram must be placed firmly (but not forcefully) in the slot. The plastic clips should snap into the sides of the ram. If you do not know how to do this, please youtube some videos of people installing ram. If you are on a laptop you MUST disconnect the battery in addition to the ac power input. Leaving the battery on will increase the chance of damaging your pc or the ram you just purchased.
open PC and see if bios has now listed your new MB of ram here
if your pc does not load up or screen turns black, but the operation lights are blinking/on this indicates faulty ram that must be removed/replaced.
if your pc turns off by itself after user is in windows this indicates poor system ventelation and could require a fan/power supply upgrade or even an indication that the motherboard does a bad job with power management. If your PC shuts down randomly, you need to keep it turned off until it cools down. Auto shutdown is a failsafe which is designed to keep your PC working when it gets overheated. Compress air your machine to remove dust. Make sure it is in a well ventilated place (not in a box or a closed cabinet). Make sure you are not running too many programs at once.
if all goes well you should be able to start taskmgr, (press ctrl + alt + tab) and see the physical ram available in the performance tab