Computer Doesn't Boot

[mydog]

Hi,
     My parents' computer has just stopped booting up completely all of a sudden. When you hit the start up button, the heat sink fan spins for a second or two then stops and the computer doesn't boot at all. No display; nothing. I took the fan off the heat sink and noticed a lot of dust on it, I cleaned it all out as well as the rest of the computer and tried again. Nothing =\ It's obviously getting power I assume because it does something when you hit the power button.
     I was looking around for quite some time on the internet to see similar problems but nothing really seems to work or I can't try what is recommended. I did pull out the 3V battery and hit the power button with that out, but same thing of course happened. I don't really know how to get the heat sink itself off so I didn't try that out. That's really all I accomplished as most of the time I was trying to find what I can do here.
     Thanks

[JJ 3000]

 How old is this machine? What brand is it? What operating system does it use?
If you cant see anything at all: rule out the monitor by swaping it out for a known good one. If you dont have another monitor, try the one in question on a computer that you know works.
The 3V battery on the mobo supplies power to the CMOS RAM which stores configuration data. You need a good working battery to ensure a stable system.
Take the old battery out and take it to your local computer store, or pharmacy,or superstore and check out the coin cell batteries.  Match the numbers on the battery and make sure that it is the right size. After you install the new one you will have to go into setup and set the date and time.
I'm no expert, so I dont know if any of this will work

[mydog]

It's about six years old now, an HP. It uses Windows XP Home, but I don't see how that pertains here seeing as it wont boot at all, I will replace the battery and see if that does help. I'll edit with a monitor check soon.

[jerryheavyarms]

Is the heat sink seated well on its place?

[mydog]

Well, I have read that the heatsink should be checked for that but I can't tell if its seated correctly. It doesn't come off or I don't know how to take it off. It did have a lot of dust in it though when I took the fan off the top and I cleaned all that out. Nothing still, but could you point me in the right direction as to how to take it off (safely if possible)? There are two little latch type things on two sides and I've tried to pull them up to release it but it gets stuck at a certain point and just stops moving. I don't want to apply a lot of pressure because I know this stuff can be all sensitive and everything. Even when the little clips/latches are pulled up as far as I think they can go it still doesn't even budge. So...I dunno. haha 

[jerryheavyarms]

Well, I think we need additional info here.. Specs of the computer please.... 

[mydog]

Well its kinda hard to figure the specs out when I can't boot up the computer. I don't know where to find the model number or anything off the motherboard. I already just took the motherboard out and can't really tell which location the model number would be.

I have 2 ram slots one with a 1 gig and the other with a 256mB..hmm
All I can tell from the motherboard is that its made by Intel =\

Re-edit: Okay just found it...mah bad haha.
http://www.intel.com/design/motherbd/rg/

[patio]

Try it without the 256 RAM chip...is the 1G chip the proper RAM ? ?

[mydog]

I have just already tried it with no ram and it didn't work still. I managed to get the heatsink off and i put it back on and now it doesn't want to turn on at all. Motherboard still gets little led lit up but it is still not turning on. By the way, in the past few hours I completely stripped the motherboard and just tried the two power wires and that didn't make it spin either. Nothing's working it seems.

[hejlik]

My best guess would be the power supply. Do you have access to one you could try? Make sure you clean the heat sink and apply new thermal paste before trying.

[saf-beagle]

My best guess would be the power supply. Do you have access to one you could try? Make sure you clean the heat sink and apply new thermal paste before trying.

Ditto. My thoughts exactly.