desk top wont turn on?

Only a single beep, does ANYTHING show on the screen?

A single beep mean a successfull POST.

No display can indicate that there is a problem with the video card, the monitor video cable could be disconnected, or the monitor may not have any power.
Check that the monitor is actualy connected to an electric outlet, is actualy turned on and that the video cable is properly connected. Try the monitor with another computer. Try another monitor with your computer.
The video card may have bacome unseated. With the computer unplugged, open the case, remove the video card and place it back in. Close the case and reconnect. Try powering up the computer.

The video card could be deffective. Try installing a spare video card. It could be an older PIC model.
If a spare video card works, you need to replace the video card.

If there is some text display. Do you get any error message like "Non-system disk, insert disk and press any key"?
This mean that the computer can't find the information needed to properly boot. It's normaly some missing or corrupted file.
It could also mean a dead drive. It's the worst case. All files it contain are likely lost.

If you only get a black display with a blinking underscore, it mean that the OS started loading, but a critical file is missing/corrupted.

For the two above, you have two options:
- Get some live Linux DVD or USB stick to start the computer with. Use the Linux environment to backup your data and downloaded application installers to some external drive.
- You may also place the main hard drive in another desktop as a secondary drive and use that other computer to copy your files to an external drive.
Once you have saved your files. Reinstall your operating system. Reinstall all drivers. Reinstall all applications. Restore your data/files.
Windows Vista and later have an "Update" option if any version is detected, even the same one. Windows XP DON'T have that option. Chosing this option should preserve all your files, drivers, installed applications and settings.

Electro
October 2013