Activation Tool for unattend_reseal.xml - repost

My name is Shawn Pierce I work at a company called STS Electronic Recycling. We refurbish older computer and send them back into the market loaded with windows 7. We are currently using windows deployment services through PXE boot. We currently are running 80-100 computers a day, and growing daily. We currently are looking for a way to activate windows while in audit mode, and have it persist through OOBE once the system has been resealed using sysprep. Currently the only way I have found to do this is to edit the [login to view URL] with code to insert the product key. The problem with doing it this way that we have found is that typographical errors can cause errors in the xml file and then the system doesnt load, and we have to restart the deployment on that machine. We are interested in a GUI APP that will only ask us for the product key and insert it into this C:\rpktools\[login to view URL] . It has to be placed on a certain line in the exact same place and the txt that is already there needs to stay. Also we would like some type of check in place that will lower some of the errors while typing the keys. I know that microsoft uses "[login to view URL]" to check if it is 5x5 key and the checksum if it possibly could be a key. The end user of this app will most likely be non technical and I would like to make this as simple and efficient as possible. We will be keying 150+ keys a day so I need the app to be able to fit onto a small usb drive and be run without installing anything on the PC.