i have emachine W3609

I went back to your first posting Barbara, to see what the problem is with your eMachines W3609 Desktop PC.

Computer crashed. Windows Vista with a fatal error.

Do you have the Restoration Disk, or did you make one? (Usually asked by Windows when the computer is new, and started up for the first time. Backup)

If so turn the computer on, open the optical drive's tray, and put the disk in. Close the tray.
When asked click on Repair. (Non-Destructive Installation)

No Restoration Disk, or you did not make a backup?

Let's go past the software problem, and concentrate on what could be a hardware problem.
(A hardware problem can cause a lot of seemingly software problems)

The two main problems with a Desktop PC is that it's dirty inside, and/or a bad Power Supply.

No slight against eMachines, but they are a budget computer. As such, they use low quality parts in some instances.
eMachines always use a low quality Power Supply.

1) Computer dirty inside.

Computer on a table unplug the power to it. Open the computer case,

Looking at the Front of the computer the Left side panel removes.
Looking at the Back of the computer, and at the left Side Panel, note the two Thumbscrews.
One towards the top, and one towards the bottom.

These are loosened. They are not supposed to come out, and be removed. They stay with the Side Panel.
Note the formed 'bump' at the end of the Side Panel. This area is for your fingers to hold onto.
The Side Panel is pulled back a little, then lifted up, and out. Lay it aside.

(The Side Panel has metal protrusions which slide into slots in the computer case.
The panel is pulled back a little, then the protrusions will clear the slots in the computer case)

Now follow Anti-Static Precautions

Anti-Static Precautions:
Your body carries Static electricity.
Always work on a computer on a table. NOT on a bed, couch, or directly on a carpet floor.
High areas of Static electricity.
Refrain from swinging your legs, especially if your table is on a carpeted floor.

Static WILL fry out (Short Circuit) the delicate hardware components inside a computer.
Relieve your body of Static BEFORE reaching inside.

Computer on a table, computer unplugged from power, computer case open.
TOUCH an unpainted surface, of the metal frame of the open computer case.
This action will relieve your body of Static.

Should you leave your computer in the middle of working on it, be SURE to Touch the metal frame again upon your return.

Use a can, or two of compressed air for computers, and clean the inside of the computer out.
You may wish to wear a dust mask.
Put the plastic straw provided on the side of the can, into the nozzle at the top of the can.
Break the plastic lock tab off of the top of the nozzle.

Keep the can as level as you can, while spraying air.
Start at the top inside left corner. Spray air across to the top inside right corner.
Spray air as a professional paint sprayer would spray paint.
Squeeze the trigger in all the way when you start. Let go of the trigger when you reach the other side.

Now drop down a space, and start again. Keep dropping down, and spraying across in rows.
You will see a fan sitting on top of a finned Heatsink.
This is the Processor fan.
Pay special attention to the fan, and finned Heatsink.
These two items need to be very clean.

You may wish to use Q-tips to disturb the dust/dirt. Just break the 'crust' so the air can remove the dust/dirt.
(You are just lightly moving across with the Q-tip. This breaks the solidified 'crust', and allows the air to remove it more easily)

When you reach the bottom of the computer case, you may wish to tilt the top of the computer towards you slightly, then use air to remove the dust/dirt at the bottom of the computer case.

The Power Supply also needs a little cleaning. Go to the back of the computer. Where the power cord plugs in is the Power Supply. Clean the fan blades, center hub of the fan, and it's surrounding cage. (Shroud)

Try using the plastic straw inserted into the Power Supply, past the blades of the fan. Use air at the top, and come down. It isn't easy, but do the best you can.

{ HOLD onto the plastic straw with one hand, and the can of air with the other hand. The plastic straw can shoot off, and land inside the Power Supply, if you do not }

Come around to the inside of the computer again, and to the case of the Power Supply.
On this end the Power Supply will have ventilation holes, or slots.
Insert the plastic straw a little into a hole, or slot, towards the top of the Power Supply's case.
Spray air moving back, and forth.

Now go down to a lower hole, or slot, unless there are only ones at the bottom. If so, go to the ones at the bottom. Spray air again. Move the straw around from left to right.
You won't get the inside of the Power Supply perfectly clean, but you will do a LOT of good.

When using the can of compressed air for computers, you will note that after a while the air pressure drops. This is because moisture is freezing in the straw, and nozzle.
Simply set the can down, and allow it to warm up for a while.

After you are satisfied the inside of the computer is as clean as you can get it, allow the computer to sit open for 5 to 10 minutes.
This will allow any moisture developed from the can of air, to dissipate.

Now close the computer case, and plug the computer back into power.
WAIT 1 minute, then turn the computer on.

Post back your findings in a Comment.

Regards,
joecoolvette