Unintentional embedded install of Macromedia Flash 8 has corrupted Windows 8 Flash player

I am in a UK school. We have just installed an older drawing package on Windows 8.1 via GPO using its MSI. Unfortunately this contained an embedded install of Macromedia Flash 8 (available to de-select in the manual install) which has installed something to make the Windows 8 built in Flash player not work (it is detected as an old version). I have now nobbled the MSI using Orca not to install Flash 8 and new installs are OK but I don't know what to do to correct the dozens or so of PCs installed with the original MSI. The drawing package uninstaller does not remove the flash 8 damage. The Flash 8 installer has clearly replaced a/some files and registry entries and they need to be "restored" with the originals. Does anybody have any ideas, or perhaps an old Flash 8 installer package I could try running to uninstall it, or a list of files/registry entries that Flash 8 has modified? Any suggestions gratefully received.