My computer will turn on, but will not boot up.  I have an integrated nvidia geforce 6100 video card.  Is my best option to try putting a new pci express card in or just assuming the motherboard is totally crashed and buying a new one?  I also have two broken pins in my connection for the COOLING fan.  Does this matter?  I didn't know if full contact needed to be made there.  Thanks. have you checked the most common causes?

loose connections on the back of your computer? make SURE everything is properly fitted into its place.....

loose cables and contacts on the motherboard? check cables from your hard drive, power cables and so on, and make sure they connect properly...

is your hard drive can be detected in your BIOS and set to boot?

is there any error message displayed on the screen?

you mean chassis fan, or CPU cooling fan?

pls let us know more...... What exactly does the computer do when you turn it on? Is there any beeps? if so, how many? Does anything show up on the monitor? How old is the pc? What brand and model? If custom build, what motherboard?
We'll need a lot more information before we can be more useful to you.Okay, sorry.  I have an emachines T3410 desktop.  The motherboard is K8MC51G.  The computer turns on, cpu cooling fan and chassis fan both start running, green light for hard drive comes on.  No noise from hard drive, no monitor communication at all.  The IT guys at work told me the first thing detected is the video card and I was going to change that, but I have an integrated one.   There is an open slot for a PCI Express card, but they told me there was a good chance that the motherboard itself was bad.  I have had some display problems recently with the monitor colors(IE the whole thing going a greenish color) so I was hoping that was the only problem.  Since I have no idea what happened, I do not know whether the rest of the peripheral hardware is still functional.  i bet that the motherboard was not defective...try removing the memory and clean the contact before plugging it again on the slot....

also make sure that the slot on your board is clean..if you are in doubt, you can replace the memory and on your system again....

hope this HELPS... My first thought was that you might have a bad monitor, since you didn't hear any beeps come from the computer (probably not the memory). What kind of monitor is it? how old? Try a different monitor.Okay, I know that the fans run off the motherboard, so it makes no sense that it is completely ruined.  The monitor test screen displays fine, just no communication from computer.  The monitor and computer are less than two years old, but shouldn't the computer boot up even if the monitor is not hooked up?  And does anyone know about the bent pin on the cpu cooling fan where it hooks into the grid on the motherboard?  I know this is not the original problem, but am curious as to its importance overall.  I may go to a small local repair shop and see about trying the new pci video card as the hard drive cant seem to get past the initial startup and I am just not good enough at this to know what is wrong.  There is no smell, nothing appears to be burnt, and nothing is bulging.  It just wont go. Does the cpu fan spin at all? If the pin is bent, but the fan still spins, I wouldn't worry about that. If the fan is not spinning, straighten the pin and try again. Take caution though, when the cpu fan doesn't spin. Without a fan, your cpu can get fried in less than a minute.