Originally posted by vekna
Hey, probably it can help you.
1) If the upgrade fails on backup stage, restart the upgrade with:
msiexec /i plesk_7.5.0_build050217.19.msi /l*v c:\plesk_7.5.0_build050217.19.log
Then try to determine the problem source in c:\plesk_7.5.0_build050217.19.log file and correct it.
2) If the upgrade went past backup stage and failed on deleting previous version stage then:
1) Exit the installer.
2) Reboot the server.
3) Uninstall previous version of plesk manually, erasing program folders and registry entries.
4) Reboot the server.
5) Rerun the upgrade with:
msiexec /i plesk_7.5.0_build050217.19.msi /l*v c:\plesk_7.5.0_build050217.19.log PLESKUPDATE="update"