The D partition is probably the Recovery Partition, used to restore the system to Factory Defaults.
Why do you want to wipe it? You will lose everything on the drive, and have to re-install all the applications and restore your data from a backup (Your friend does have it all backed up, correct?)
It will also remove the ability to use the Recovery Partition.
The hal.dll problem is usually an easy fix. Follow the steps here:
Missing Hal.dll