I'm building a PC with an ASUS P8H67-V mobo. It has two PCIe2.0x16 slots (SLI ready). I'm going to use ONE slot for a video card (ASUS GT430 128bit). My Power Supply (600W) has a 6-pin & a 4-pin cable connector, not a 6+2.
If I'm only going to use one PCIe slot, would the 6-pin be adquate?
The number of pins required (6, 4, or 6+2) on the PCI-E power cable depends on how many are required for your graphics card.
Looking at your ASUS GT430 128bit graphic card's specs at the link below, it does not require a extra power connection with a PCI-E power cable, so you do not need to worry about it.
According to the manual for your motherboard it should be OK with just the 4 pin in the CPU (ATX12V) connection,
seeing as the ATX 2.0 spec only calls for a single 4 pin CPU connector. All things considering if your power supply is that old I would consider looking at a new one that is up to the current specs (ATX 2.3).
We thought you were referring to the power connection on your graphics card.
Stormy (Richard) is correct that you could use either a 4-pin or 8-pin ATX +12V power plug. This is to power your CPU. Just be sure to plug it in on the side (right side on diagram above & below) closet to pin 1 on the motherboard's 8-pin (EATX12V) power connecter.
It's just that a 8-pin is recommended to be able to provide more power if needed for the CPU say if it was more powerful, under a heavy load, or overclocked. That's all.