How do I delete a factory installed compaq partition and reclaim the space under the C drive?

I have a Compaq Presario running Windows XP Home. This has a 150GB hard drive installed. My user files are stored on C: which have 143GB and I believe the XP data files and system recovery were stored on D:which have 7GB. I made a backup of the D: onto 2 dvd's and deleted everything that was in the partition. I want to erase the partition altogether and simply reclaim the extra 7 gigs under my C: Drive. I have a Copy of Windows XP Pro that I plan on installing and i want to make use of the whole HDD without any partitions on it. I've tried to do the same on another Compaq Pc and after install of WinXP Pro..I still ended up with the sepperate Partition. Can Someone PLEASE EXPLAIN to me...STEP BY STEP...how i go about reformating the whole HDD including MBR...SO I can have a fresh install of WinXP PRO...without the wasted disk space and partition. All Help and Links would be greatly appreciated. The more information I have at my disposal, the better..no such thing as too much info. Thx

How do I delete a factory installed compaq partition and reclaim the space under the C drive?
Unfortunatly Windows xp cant see any thing more then around 137 to 143 gigs per drive It has something to do with the way windows formats the drives. I know this for experiance I would love it if there was a way i could do that with my 250 gig drive but NTFS formating and Fat32 prevent it from happening.