[SOLVED] Installing Windows XP Over Vista?

hi..
i have a HP pavilion a6450 desktop.

My chipset is nforce630i.

it has a 320GB 3G samsung harddisk with two preloaded partitions.

C:289GB and DFactory_Image)9.02GB

I tried to install XP with XP installation CD...

While doing so in the option for where to install XP i was shown a partioned space of only 131GB out of 320GB.

Anyhow i continued the installation by partitioning the 131GB into 4 drives using NTFS.

Everything went fine and i found out the drivers for the hardwares and installed except for 1 Exclamation in Device Manager for PCI Bridge.

Now is there any way i could recover the rest of the space (around 170GB) of my hard disk without uninstalling XP?

When i unzipped the setup file of my chipset there were files for RAID, SATA-IDE and SATA driver files(hope these are the driver files). Will it be useful in any way? If so how can i use them?

kindly help me.... thanks in advance.