I was given this monitor(C 593) without a voltage cord - what do I need to look for?

Yes. But you'll need a different power cord:
The monitor power supply is provided with Automatic Line Switching (ALS).
This feature allows the monitor to operate on input voltages between 100-240Vv, 50/60 Hz, 1.5A.
The power cord set (flexible cord or wall plug) received with the monitor meets the requirements for use in the country/region where you purchased the equipment.
If you need to obtain a power cord for a different country/region, you should purchase a power cord that is approved for use in that country/region.
The power cord must be rated for the product and for the voltage and current marked on the product's electrical ratings label.
The voltage and current rating of the cord should be greater than the voltage and current rating marked on the product.
If you have questions about the type of power cord to use, contact your HP-authorized service provider.
A power cord should be routed so that it is not likely to be walked on or pinched by items placed upon it or against it.
Particular attention should be paid to the plug, electrical outlet, and the point where the cord exits from the product.

you need a vga cable

http://www.12vadapters.com/ Higher current rating is OK but not the voltage.

If you run windows 7 you will not have the driver for it since its too old, XP should be OK without the driver.

Basic LCD monitor troubleshooting guide:
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://en.wikipedia.org/wiki/Capacitor_plague

It may have failed Backlight inverter circuits. You just need power AC cord and the VGA cable to attach to the PC VIDEO card. Try it on another PC.
http://s807.photobucket.com/home/budm/allalbums

this model is known for problems os you have one or two things you can do; 1. get a new lcd monitor orget that one fix at the cost of a new one.

Speakers don't work on monitor

Any Computer Electric Plug Will Work But The Cable For The Screen To Hook To The Computer Can Be Bought On Ebay, Circuit City, Radio Shack, Best Buy Wal-Mart Even.

the HP part number for the US power cord is
8121-0740the part number for the US power adapter is
5189-2852

Is your monitor a CRT or LCD type. For CRT type information follows. In most cases your simptoms indicate a problem with the High Voltage or blanking circuits. Caution the High voltage can be as much as 40,000 volts and even unplugged from the wall the picture tube can continue to hold voltage (enough to hurt you). Do you here a snapping sound from the back of the crt. If you do the high voltage is shorting out and the protection circuit is turning off the high voltage. If you do not here sparking another possible cause is a faulty capacitor in the protection circuit or the flyback (high voltage transformer). Unless you are educated in electronic circuit repair this one is probable beyond your curren knowledge level. You can try taking the back off and cleaning out all the dust, but remember to stay away from the red wire that goes to the picture tube. Use only non metal cleaning tools. Good Luck

Nssms

The screen comes standard with a LiteOn power supply, 12v 3.3amp