We save upgrade status in the old cache dir.
This is potentially problematic - what if upgrade is "in progress" from multiple hosts simultaneously and these hosts have dynamic IPs?
What if this old dir is read only and we can not save status there?
What if this old dir is "slow" (not sure if roaming profile supports "copy on demand"), then check may become very expensive and we are doing it forever.

(igor) I think we better use registry for this as upgrade it windows only.