Fit desktop RAM safely

The physical fitting, the slot order that catches people out, and what to do if it will not boot.

Safety level: caution · Time: about 25 minutes · Level: beginner

Applies to

• Desktop PCs with accessible DIMM slots

You will need

• The correct memory kit
• A Phillips screwdriver for the side panel
• A well-lit table

Fitting memory is one of the easier upgrades, and there are exactly two ways it goes wrong: static, and the slot order.

Applies to

Desktop PCs where you have already confirmed the generation, capacity and free slots. If you have not, do that first — buying the wrong generation is the most common wasted purchase we see.

Before you start

• Shut down fully and unplug the power cable. Not sleep. Not hibernate. Unplugged.
• Hold the power button for five seconds with the cable out. This drains residual charge from the board.
• Discharge yourself by touching bare metal on the case before touching a component. Memory is genuinely sensitive to static, and static damage is invisible — the stick simply never works, and you cannot tell by looking.
• Work on a hard surface, not a carpet or a bed.

Steps

1. Open the side panel. Usually two thumbscrews at the back. Lay the case on its side, board facing up.

1. Find the DIMM slots beside the processor cooler. There are two or four, with clips at one or both ends.

1. Check the slot order in the manual. This is the step people skip and then spend an evening on. With two sticks in a four-slot board, they almost always go in slots 2 and 4, not 1 and 2. Filling the wrong pair runs the memory in single channel — the machine works and is measurably slower. The board manual states the correct pair.

1. Open the clips on the slots you are using.

1. Line up the notch. Each stick has an off-centre notch that matches a ridge in the slot. It only fits one way. If it does not drop in easily, it is the wrong way round or the wrong generation — do not force it. DDR4 will not fit a DDR5 slot and forcing damages both.

1. Press down firmly and evenly on both ends until the clips click closed by themselves. This takes more force than feels comfortable. A stick that is not fully seated is the single most common cause of "it will not boot after I added RAM".

1. Check the clips are closed on both ends of every stick.

1. Replace the panel, reconnect, and power on.

Expected result

The machine boots. Task Manager → Performance → Memory shows the new total, and the slots used reflect what you fitted.

To get the rated speed rather than the default, enter the BIOS and enable the XMP (Intel) or EXPO (AMD) profile. Without it the memory runs at a slower default, which is not a fault.

If it does not work

No display, fans spin. Almost always seating. Power off, unplug, and reseat each stick — press until the clips close themselves.

Boots but only shows the old amount. One stick is not seated, or is in a slot the board does not populate in that configuration. Check against the manual.

Boots with one stick but not the other. Test each stick alone in the same slot. A stick that fails in a slot the other works in is faulty; bring it in.

Board shows a diagnostic light or code. Look it up in the manual — most boards have a memory-specific indicator, which tells you immediately whether it is a memory problem at all.

Stop and ask a technician if

• Anything smells hot, or you see or smell scorching
• A slot clip has broken off
• The machine was working and now shows nothing at all after several careful reseats
• The machine is under warranty and opening it would affect that

Bring it in. Diagnosis of a machine that will not post is quick for us and frustrating alone.

Typical turnaround for a memory fitting and test at the counter is Same day or two days.

Read this next

• Work out what RAM your desktop can take — Check the module is the right one for your board before you open the case.
• New memory is not detected, or the PC will not boot after fitting it — If it is seated and the machine will not start.
• DDR4 or DDR5: which do you need, and does it matter? — What the generation on the label means.

Still stuck?

If anything here does not match what you are seeing, stop rather than force it. Contact us · Book a repair

Last reviewed 2026-08-30.

Written by Krishna Patel for RJ Digital Alliance, 30 August 2026