I am not enough of an OS expert to even know what to ask you. I think the 2.9x DVDFab used ASPI to access the drives, the newer versions use SPTI, where you may have a conflict with some existing software. If you can get DVDFab to open and run, see if you can get to Common Settings and change the I/O control from AUTO to ASPI. At this point I believe I would uninstall v4 and v5, run a registry cleaner, and try again. You should try to start DVDFab with no disc in the optical drive; if there is a DVD in the drive it will immediately try to use the SPTI layer to take control of the drive to read the disc and if this is not possible it may lock/freeze etc. This basically informed guessing here until someone better at OSs comes along. This is an unusual symptom.