Boot Failure Heat related problem

You can take the PC outside and use a can of compressed air to blow away the dust.

Make sure to blow out the power supply. (Box that the AC power cord plugs into.)

Then, power up the PC with the case open and make sure that all of the fans spin. Any fan that does not spin up or spins very slow needs to be replaced.

As to additional fans, that depends on your case.
If there is a grill type series of holes with a square pattern of screw holes around it, you can install a case fan.

Otherwise, the easiest fan to install is a "slot" fan. These fit into a standard size PC slot.

Since you are not hardware savvy, I recommend that you take your PC to a small local PC shop. Many of them will install a fan while you watch for just a few dollars more than the cost of the fan. Plus, they are very willing to educate you on PC hardware.

With the heat problems you have had, it is VERY possible that the CPU or power supply has overheated and is failing. A good repair shop can run some quick diagnostics for you to let you know if the cleaning and new fans have done the job, or if you need to replace hardware.

Chas

There is something else that I've seen a few of recently and that is the North Bridge Chip going bad. This should have a Heat Sink on it but no fan or any other cooling device and unless you know exactly what it is you are looking for it's really the job for a PC Repair Shop and requires a replacement M'Board and possibly a CPU & RAM as well depending on how old the M'Board is.

There should be a Black or Gold looking square Heat Sink below the the CPU and roughly behind the Video Card Slot or PCI Slots if the Heat Sink is Loose the M'Board needs replacing but you need to be extra careful before touching this as any Static that you have built up on you can destroy a otherwise perfectly good M'Board so if you really want to have a look unplug the case and place both hands on the metal of the case to discharge yourself or at the very least bring the case and everything earthed to it to the same potential so there are no Static Discharges occurring. If you can wriggle this Heat Sink the M'Board is most likely shot and needs replacing.

Col

You are going to need to invest in a can of air to blow all of the dust out of any fan that you may have in your case (you will see them), on your motherboard (you will see them as well), and in your power-supply (usually on the top of your tower, or the bottom of your tower. Look where the power plug goes into the computer).

After this is done when you have the cover of the case open, you will be able to look in at the motherboard (the largest component in your pc. It is flat, will lay against the back wall, and everthing plugs into it.) Some where towards the center of the motherboard you will will see an aluminum spikey deal. This is your heatsink and it sits on top of your processor.

There will proabably already be a fan installed on top of this. If there is a fan on it you will want to power up the pc to check if it will spin. This may be your problem. If it does not replacing it is very simple and inexpensive.

There will be four screws on the corners of the fan housing and a set of power cables that will plug into either your mother board or one of the power adapters from your powersupply. Unplug and replace. If there is still a heat issue you shoud try the case fans and maybe put some thermal gell between your heat sink and processor.

I hope this helps.

Travis