I Have Vistsa First When I Do Xp Set Up It Says That It Cannot Find My HardDrive?

Most newer computers use SATA drives. This means that you must install the third party drivers for the SATA controller built in to your motherboard.
Go to manufacturer's site and under support/downloads/drivers using your model of computer you will find the SATA driver. Be sure to read the download and installation instructions as these must be set up either on a floppy or VD using a program called "Make Disc"

These can also be found on the motherboard drived CD that came with your computer...

Once the drivers are properly prepared for installation....re-boot the installation CD and follow the prompts.....to install third party drivers press F6