I think Touchwithran has misread your post. His advice might be excellent, if only your computer was running - but it isn't !
There are two or three reasons for your computer not going past the boot screen, let's take a couple of them that do not require opening up your computer !
You are getting to the BIOS screen, so, press 'F2' while you can see it. This will bring up the BIOS system. Using the arrow keys, move along the top to a tab that says 'Boot priority' or something similar, and ensure that your hard drive is the first item in the list. You do this by using the up and down arrows to select your hard drive, press 'Enter' and then you will see instructions in the extreme right hand panel as to how to move your HDD up the list, if necessary. Normally, it is a matter of using the '+' and '-' keys. Then exit and save your changes, and see if your computer boots itself.. If it does, great.
If it doesn't boot itself after the above, but sits at a black screen with a blinking cursor, shut it down and re-boot. Then, at the BIOS screen, press the 'F8' key. This will bring up a menu of the drives attached to your computer in a form like : CD/DVD drive ( type No), HDD (type No.), HDD (type No.) [ if you have more than one HDD], USB drive(Type No). Again, use the up and down arrow keys to select the hard drive that has your Windows on it, then press enter. Your computer will start itself up again, and this time, hopefully, boot. Again, if it does, great.
If neither of these work, then it is probably time to have a look at your RAM just to make sure that it is properly seated.
If you have the Windows install disc for your computer, you can try to see if it will boot from that. If you don't have one, you can make a bootable repair disc from any other computer running Win 7, see below for instructions.
Power up the computer, open the CD tray, put the disc in, turn off the computer and re-boot with the disc in the drive. follow the instructions and see where it gets you to.
If any of this solves your problem, great. If it doesn't, post back but include details of your computer - make, model etc.