Tony2886,
Please create at least one set of HP Recovery Discs, if the computers didn't already come with them.
Assuming the Pro 3500's came with Windows 7 Pro and have a v2.1 SLP/SLIC;
What type of server based image are you trying to deploy??? If it is based on a VLK or the like, there is no need to use ABR.
If the server based image contains no product key, then you will need to run ABR to recover the OEM SLP key and certificate off of one computer only.
The HP Pro 3500 Desktop Computer is a business class computer and as such, your questions may be better answered in the HP Business Support Forum.
Please see HP Business Support Center - Get help from HP to contact HP with your support questions.
Please click the white KUDOS star to show your appreciation