On a new computer with a 120gb HDD the Vista Home Basic installation was in 3 Partitions, OEM (1gb) - Primary including the OS (34gb) 'C' Drive - Primary Partition (77gb) 'D' Drive. With diskpart I have selected disk '0' from 'list disk' using 'select' command, then the 'extend' to to have a single partition for the whole drive. List Disk is now showing 'Disk 0 112gb'. Under 'List Partition' it is still showing 3 partitions - Partition 1 OEM (1gb) - Partition 2 Primary (34gb) - Partition 3 Primary (77gb). How do I extend Partition 2 to include Partition 3 in a single partition? The file system on both partitions 2 & 3 is NTFS. Help!!

I personally would recommend leaving them alone. My machine is divided as well into three, but for a reason. "disk 0" in question is your first partition (OEM).

Did you restart your computer by any chance after this? If your MBR and all that is being used, you really can't change any of that stuff, as your system will break.

Is there a reason as to why you want to mesh your partitions together?

You can't change partitions that are in use by Windows - it won't let you do this without a reboot.

Recently I've noticed a lot of OEM's placing a small partition at the beginning of the hard drive - I presume it's for boot purposes (and their special tools). Along with this will be an OS partition and a recovery partition.

Messing with the initial small partition may cause your system not to boot - and may break any of the programs that are installed them.
Messing with the OS partition generally won't cause any problems as long as you're expanding it - shrinking it can cause issues tho'
Messing with the recovery partition can make your system non-recoverable in the event of a disaster - not (IMO) a good thing to do.

What's the make and model of your laptop so we can figger out which is which?
With the price of external hard drives being fairly inexpensive, I'd suggest leaving things as they are and using an external drive to store the extra stuff. I currently have Vista Ultimate installed on an 80 gB laptop and still have plenty of room on it (I don't do music or movies tho').

If any of the partitions that you are wanting to join or merge are set as "active", then you willn't be able to perform the task of bringing them together