The only difference between HP2A and HP2 is that HP2A has an updated bootcd.iso. HP2 accidentally had the HP1 bootcd.iso
(ZDM7SP1_IR1_HP2_20080131.zip and ZDM7SP1_IR1_HP2_IMG_Resource.zip had the hp1 boocd.iso)

If you are using PXE for imaging SP1 Hot Patch 2a or newer must have been applied or the server will have to be updated to IR1 HP2a prior to using the PXE resource files from ZDM7SP1IR1_HP2a_Img_Resource_Files.zip. If a quick test is needed to see whether the hardware will be recognized by the ZENworks Imaging kernel without any update to the ZENworks server, use the bootcd.iso first for the testing of the hardware.

This Hot Patch requires ZENworks 7 Desktop Management Support Pack 1 Interim Release 1. For other system requirements, see the ZENworks 7 Desktop Management Documentation
It is not necessary to apply previous SP1 IR1 Hot Patches prior to installing ZDM7SP1IR1HP2a. 

More details here .