Can no longer run program

I've done a series of system roll backs over the last week and now I cannot get any Corel program to open.

I've un- and re-installed twice but this has not helped.

I can see my .cdr files and their previews in Windows 7 but when I double click on one I get the error message "there was a problem sending the command to the program"

Is there something I need to do for a clean uninstall so I can reinstall correctly?

Or can someone suggest another solution?

Thanks in advance for advice,

Jo