Thank you demhaizar and Bert,
Dr. Razi's link above fixed a similar problem that I was having.
I thought it might help some other poor unfortunate in the middle of the night or weekend, so I will attempt to elucidate.
After other install errors to be described below, I, too, got the following error message on some, but not all, of my computers:
"Package Microsoft XML Parser 4sp3 Error: The specified account already exists"
The affected computers also had installed a billing program using SQL Server Express 2008R2 and included a Crystal Reports runtime which also snafued the AC7.1 upgrade (from 6.5).
Download msxml.msi and the associated .cab, right click on msxml.msi and select uninstall. After that, proceed with the Amazing Charts 7.1 upgrade. I was then able to reinstall msxml. Right click msxml.msi and choose either install or repair (I chose install, but it redirected me to repair). AC7.1 worked fine after the reinstall (repair) of msxml.
The other upgrade problem involved SAP Crystal Reports. Amazing Charts 7.1 upgrade refused to install over a newer version of SAP Crystal Reports runtime. After uninstalling Crystal Reports runtime engine, the upgrade still failed. I had to also uninstall the application that was using Crystal Reports (PB Clinic). After doing that and the above msxml tricks, the version 7.1 upgrade proceeded without problems. I was then able to reinstall the billing application and Crystal Reports (as well as msxml). All seems to be working well at the moment, I will update this if problems crop up.
Don
