Can't Do Upgrade To Fix Updates Not Installing?

I've a customer who simply cannot install all updates. In in the end, he decided to try the upgrade route in an attempt to fix the updates not installing. He got hold of an ISO (without SP1) and started the process. At about 70% completion (I believe the OS components have successfully been installed) it stops. The error message states something about lack of disk space to install the applications (????).There's plenty of disk space of coursePrevious to the upgrade try, we've run various MS FixIt tools, SFC, disk check, disabling A/V, checking for malware, etc. Commonly, upon unsuccessful updates, the error codes are either 8007371b or 80073712.