Installing a DIMM in your desktop

Non-magnetic screwdriver (for opening your case)
Your computer manual
Step 2: Ground yourself.

Static electricity can damage your module and other computer parts. You need to ground yourself to avoid "shocking" your computer. If you have wrist straps designed for this purpose, you should wear them. If you don't have wrist straps, here is the easiest way to ground yourself:

Turn off the computer, monitor, and all accessories (printer, speakers, etc.)
Leave the computer power cord plugged in. (It's OK to unplug your accessories if you like.)
Briefly touch an unpainted metal part of your computer case.
Plant your feet and don't walk around. If you do need to walk around, ground yourself again before touching any of the internal parts of your computer.
Step 3: Open your computer case.

Every computer case is a little different, so consult your manual if you have any questions about how to open your case. (Note: The memory for Apple iMacs is installed in the back of the monitor. Your iMac manual and the Apple Web site have instructions for opening your system.)

If you haven't already done so, turn off the computer, monitor, and all accessories (printer, speakers, etc.)
Remove any screws holding your cover in place.
Remove the desktop cover.

Step 4: Find the DIMM slots.
DIMM Slots
DIMM slots are usually black; there are ejector clips at each end of each slot.

DIMMs fit into slots that look like this. Some of your slots are probably already filled with modules.

Tip: If you have a minitower system, it may be easier to install your DIMMs if you lay your computer on its side.

Step 5: Remove the memory you are replacing (if necessary).

If you have an open DIMM slot, skip this step and go on to Step 6. If all of your DIMM slots are full, you will need to remove one or more of your old modules before you can install the new memory.

Press down on the ejector clips on either side of the module.
Remove the module from the slot.

Step 6: Install your new module(s).

Take your module out of its anti-static bag and hold it by the edges.
If you have more than one open slot, fill the lowest numbered slot first. If you can't see any numbers on your motherboard, use the slot that is closest to the filled slot(s).
Line up the notches in the row of gold pins at the bottom of your module with the keys in the DIMM slot on your motherboard. (If the notches don't line up right away, flip your module around and try it the other way. It doesn't matter which side of your module has the black chips or the stickers on it. The important thing is to line up the notches.)

Line up notches
Notches on the module fit into keys in the slots (circled).

See a different angle. Place module in slot
Ejector clip is still in "down" position.

Use your thumbs to press the module into the slot. Press hard! It takes about 20 lb of pressure to get the module properly inserted in the slot. When you hear a "click" and both side ejector clips snap up around the module, you know it is installed correctly.

See a different angle. Push Hard
When the ejector pins snap up around the module your memory is installed.

Tip: Try to avoid touching the gold pins at the bottom of your module. You probably won't harm them if you do touch them, but it's better to be safe than sorry.

Step 7: Test it.
Before you close your case, turn your computer back on. You should see the new amount of memory displayed on your startup screens or in the properties for "My Computer" (if you use a Windows operating system). If everything works correctly, skip to Step 9. If not, go to Step 8.

Step 8: Troubleshooting

If you have trouble with your new RAM, check these things first.

Check the power cords. Is everything plugged in properly?
Check the module. Did both side clips pop up to hold the module firmly in place? Try removing the module and replacing it to make sure it is seated properly in the slot.

Check the clips
If your computer doesn't recognize your new RAM, check to make sure the ejector clips on each end of the module have snapped around the module.

Check the wires and cables inside your computer. Did you accidentally bump one of the cables inside your computer while you were installing your module? A loose hard drive cable can prevent your computer from booting up properly. Make sure all the cables are firmly in their sockets.
If you're still having difficulties with your RAM, check the Crucial FAQ section. You may find an easy solution for your problem.
Step 9: Close your case.

Congratulations! You have successfully installed your new RAM! Now just put the cover back on your case and plug in your accessories. Your computer should be speeding along in no time.

From www.crucial.com