I am stubborn and still using CS5.  I've had a couple new hard drives and a challenging Windows 10 update.  But, just before Windows 10 update - Illustrator stopped launching.  It used to say something about a missing registry file, but now the Illustrator badge pops up, it will say cannot complete the requested operation and disappears within a couple seconds.

I use Photoshop, Bridge and Lightroom every day.    Also InDesign still launches.

Anyone know if I have to uninstall everything and install again?  Or do I just pop the disk in and run a .exe file from an Illustrator folder.  I'm afraid to do too much in case I mess up Photoshop and lose all my presets. 

Yes, it's a legal copy.  No I don't want to go CC (yet) and I don't use Illustrator often enough to pay what they ask for it on CC.

Thanks!  (I'm turning into my 90 y/o mother, afraid I might break the computer if I push the wrong button

Thanks but I can't launch the program to reach the edit feature    Modify.... I'm now reading the rest of the help article.

If you have the original on disk, try a fresh reinstall. Then go to properties and maybe dial it back to an earlier version of Windows. There are also other things you can dial back in the properties too.
To go to properties, right click on the Illustrator thumbnail then choose properties. There you should see things such as earlier versions of Windows. Try messing around a bit till you get Illustrator working decently. Should work but some things may not work but its usually nothing important that would make your program useless. 

Did you guys know that if you try to uninstall and install Adobe software from the time we bought boxed versions and upbgrades too many times without deregistering first, it might stop working and you have to contact adobe to unlock? I dont remember if is six times or more.

In any case i had been buying upgrades ever since CS3, I had the boxed version...And I noticed that I only have left maybe one install...
I never knew about deregistering, and many hard disk crashes didn't let me do it when I had found out about it...

So basically, when you try to launch it gives a message ...sometimes You have to contact adobe to help unlock.

I dont think this is a problem with the Cloud these days.

Yes I was aware of deregistering, but I haven't had to reinstall that much. I don't consider it enough of a reason to go back to CC.

If that's really the case, that really bites. 
Shouldn't it be that if you purchased the original on disk, you should be able to use it as you please? Since after all you own that copy.  With the exception of not using it as intended of course.

The license for the software allows you to use it on 2 computers (I think). If you keep reinstalling, Adobe thinks that you might be installing on a bunch of different computers, when in fact you are probably just reinstalling because of corruption, a new computer, or other legitimate reasons. I was never bothered by that, I understood they had to keep some sort of control. Far better than paying a subscription.