Hi Hoggie,
You need something like this if you don't have a PCI 6 pin connection.
[ATTACH=CONFIG]2462[/ATTACH]
It uses 2 SATA connections from your PSU.
There is a Molex version too if you have Molex connections.
They cost around £5
If your OS is still XP you probably have Molex connections from your PSU.
They look like this:
[ATTACH=CONFIG]2463[/ATTACH]
Google ....pci 6 pin adapter
Add SATA / Molex depending on what you need.
You will need 2 spare connections for the adapter.