I have 3 wires on my pc and i dont know where to connect them on my motherbaord - the wires have writen on them "HDD LED" "PWR LED" "PWR S/W" can any1 help me?

Hi Dan,
The wires are from the front panel. HDD LED which causes an led (usually red) light to turn on when the Hard Drive is active. The PWR LED turns on an LED light (usually green) when you turn on your computer. The PWR S/W turns on your computer when you press the on button of your computer. The front panel connector riser is usually located on the bottom right of your computer. They fit on little pins. Unfortunately there is no standard, so connections vary. Sometimes the pins are labeled on the motherboard. . Check your manual. For more info do a google search for "Motherboard front panel connectors". Hank

Harddisk (access) LED, Power LED and power button...

There is a pin header on the motherboard to which this cables have to be connected. It usually is located near the lower right corner of the board (assuming that the external connectors are facing left).

Check the manual of your board for the pin assignment. The connector usually is called PANEL, SYSTEM PANEL, FRONT PANEL, etc.
The HDD LED may also be referred to as IDE LED in the manual.
Take care about the polarity (+/-) of the LEDs.