nothing happens when i turn on my computer. all lights come on and stay on. but nothing boots up. why?

K, so I'm bettin this prob occured after you installed the new vid card? Shut down, plug the monitor back into the onboard video and see if it boots. If so, you need to install the driver for the new card, go into device manager and disable the onboard video, shut down, put the connector in the new card and reboot. Hope that works!

Sounds like you will be purchasing a new hard drive! It used to be (not knowing how old, or young your computer is) that PC hard disks did not automatically park their heads when shut off. If this drive isn't spinning up, putting it in the (this is one of us techies weirdest fixes, but I swear it sometimes works) freezer for about an hour will usually get the drive spinning again so you can copy needed files before the drive warms up again. The first thing you want to do is run a disk utility like Norton disk doctor, or wddiag (if it's a Western Digital drive), or maxblast (if it's a Maxtor drive) to verify whether the drive is working mechanically or not. If it is a master boot record problem, sometimes running Fdisk/mbr will correct the problem. As an A+ PC technician I have seen this problem many times. Usually if the drive is not making a clicking sound you can be successful in recovering the data.

Is your monitor on? LOL a simple answer. Also make sure it is plugged into the wall and into the computer in the correct slot.

But if you are sure it is, your new video card may not be installed right. I don't know a whole lot about video cards but someone else may be able to help you.

Does it beep. If it beeps more than one, write down the sequence including long and short beeps and spaces. Then you should be able to look up BIOS Beep codes and find out which part of your computer is the problem. If you did add new hardware, yeah, remove what you've added and see if it works then.

It has a new video card...Is the old one on the motherboard? Did you try hooking it up to that one and see if you get picture?

If so, then you may need to disable the on-board video card for the other one to start operating.

does you motherboard have an onboard graphics chip? you need to disable it if your using a grpahics card. also check that you have connected all the case wires correctly to the motherboard. this is a common error made when building pc's

The power supply is damaged. You shouls have the power supply checked and tested for a short fuse.

If you don't even see the post, it's most likely that you have a motherboard problem or CPU problem.

Search Overclock.net. This is a common problem.

The monitor is plugged in and turned on?