I have completely removed any trace of PSP X4 that I could find and also deleted all references to X4 in the registry. I do have other Corel products installed so don't feel inclined to delete these. If that should be necessary, then I judge PSP X4 an absolute failure. I had no problem installing and running the beta on the same machine, but the final release has proven impossible so far.
I don't know how to repair from the install disk. I am presented with no such option and can find no utility on the disk.