First you need to know what type of harddrive you have or the original model of the computer to determine if you have a SATA ot IEDE controller for your harddrive.

SATA drives need third party drivers installed during the set-up process which must be installed using the F6 method of installation. These drivers must be on a different media than what the installation disc is on. They usually come from the motherboard driver CD or from the manufacturer's website and have explicit instructions for installation.

1) Boot to the Vista installation CD and follow the prompts closely
2) set-up starts and you are prompted to install third party or SCSI drivers by press F6 If you do not need this then do nothing
3) Set -up inspects the drive (if set-up finds no drived installed then you will have to start over and use the F6 option to install the drivers.
4) Set -up finds the harddrive and shows all the available partitions and prompts you as to where you wish to install vista or delete the partitions.
Highlight the partition and choose to remove (delete) and follow the prompt to do so by pressing the L key. Do this for each partition shown till there is just a total unallocated partition or 1 single space designated.

Note Here is where you need to decide as to you wanting to repartition your harddrive. I personally don't like large partitons and drives and partition mine into smaller units depending on the size of the harddrive. I keep 100 gig drives or less as single partitions. On larger drives I partition them to smaller sizes. You only need to select the first partition at this time. To choose the partiton size select to create partition size.

5) choose to create the partition and set-up will do the rest including formatting the partition.
6) Just follow the prompts and when finished you will have a clean installation of vista.
7) you will then need to install all the missing driver files and then visit windows update to get the security patches and all that.
Once finished you use the disc managent program to sub-divide and partition the rest of the drive if needed.