A bug to stop me from reusing it - that might well be the case, thanks Cactus Music. I did let it expire without registering.
 
I will contact Cakewalk support and they should know the remedy if this is the case. I can't re-run the Trial because even it won't install now.
 
Just checked my System and I am on Service Pack 1. I forgot that I put it on a while back. You've scared me away from updating further, Cactus, so I might just hold back from now until I hear back from Cakewal support.
 
If problem not solved I will give system details as asked by Bob Bone
 
Thank you all

Yes this is a job for support and they are very helpful with this type of issue. From what you've explained I see no reason to suspect your computer at all. 
 
Do you have a second computer? You can install Sonar on other computers as long as your the only one using the program at a time. 
 
If this was a computer you used for internet surfing I would highly recommend the updates. From what I see 90% of the updates are all security related which for most is very important, My DAW will not see the internet for another year if I can help it. To run Sonar all you need is to make it to the desktop. 
But don't go by me I'm just real pi--ed that the updates cost me so much time wasted and with nothing improved for me at all. They also ate up 2 gigs of bandwith between my 2 computers and I pay $10 a Gig on my provider ( Telus G4 ) The worst updates where Office 2010. And then the Not Genuine Notice?? I had to phone microsoft to get rid of it and they didn't even apologize for the mess. 1 hour also wasted. 
 

Sorry but you are far more likely to run into issues if you don't update than if you do nowadays. There have been a ton of library updates and fixes since SP1. I would not deter yourself from updating windows. Backing up is always important as well. The main point is to get the software dependancies up to date before moving further (such as C++ library) and this is quite a legitimate initial course of action before you move onto the next step.

Issues with windows updates are quite rare nowadays I would not rely on one persons misfortune. Microsoft do not release updates in order to make things worse.

BTW computer definition of a 'bug' is something that is unforseen not something left on purpose. With a clean uninstall, cleanup and reinstall any residue should clear. But we are exploring other options first (a procedural order ruling one thing out after the other, right now there is absolutley nothing to give any real diagnosis of what is happening here).

Cheers.

Hey Alex, if you can point me to one of the updates that will improve the performance of Sonar, I'll download just that one update. My guess is there are none. It's all updates for security and other system toys I don't use. 
Update Sonar.. yes
Update Drivers for Audio interface .. yes
Update Drivers for  Video card... yes
Update Drivers  for my Mobo ... yes. 
Update Windows????? why
Install Windows 8.1 .. better idea yet. 

Cactus you need to understand about software dependencies here. If you aren't on the latest libraries for instance things can go quite wrong (ie C++ libraries). Maybe a windows install component needs updating. There are probably 100's of updates and many of them fixes and performance updates(performance updates are normally optional). You don't need to guess what fixes are for, all fixes come with documentation. Tainting all fixes under one brush isn't a good idea. MS withdraws buggy fixes anyway in the rare event. We've all been giving quite standard advice here which has been tried and tested.

Certainly no harm with ringing up Cake.

I do understand, and please no offence intended here, as you are the last one I would wish ill feelings towards, But   I see nothing that would improve the performance of an already smooth running Sonar set up. C++ is important to your initial install, and this could cause the OP an issue, but what I'm saying is once you've built your system and it is running smoothly I feel the updates are of no value to my DAW. Just me, and once burned as they say, I'll not be updating again. Next move is Windows 8.1 for the DAW. 

Don't know much about C++. Is it an automatic windows update if I turn the windows updater on, or is it something I have to specifically go find and download manually?
 
(I've written to Cake support. Don't want to ring them cos here in Australia the 5 hour window of them being open is way past bedtime and way before rise time. Yes, I am lazy.)

It is an update, but if yours was wrong the Sonar installer would tell you it can't install period. 
You seem to have no problem installing, right? Your just locked out of your software. 
The behavior you get is what I  got when I'd try and run my X1 demo I downloaded a long time ago. It used to flash a box that needed the registration code.  then it just stopped loading at all. I uninstalled it , but it seem to keep a few pieces hanging around. Like Bob said, totally obliterating some software is complicated! 
 
Of course the extreme solution is a OS re-install as that would rid your system of the demo time out bug. 

Don't worry about C++ right now,no fault has been diagnosed yet. I would follow Bob's advice here to the letter here and get a nice base to uninstall, clean up and reinstall if necessary.

"It is super important to have Windows 7 maintenance up to date."

+1

Bob is also asking for specs and Scook had an earlier post about complete removal and reinstall.

robert_e_bone
At a bare MINIMUM, Windows 7 MUST have Service Pack 1 maintenance applied, due to Sonar dependencies on redistributable routines that only become part of Windows with that set of maintenance.
 
It is super important to have Windows 7 maintenance up to date.
 
Let's start with the above, and then we can dig into whatever is happening beyond that.
 
Please also list the details of your system's specifications, so that we know what we are working with.  You can look at my signature at the bottom of this post for an idea of what to list, or someone else's.
 
Since there are NOT widespread reports of Sonar failing to install, it is QUITE likely that we can get this figured out and get you up and running.  X3 is actually regarded as extremely stable, and one of the best releases they have ever put out, so I firmly believe this to be a solvable situation.
 
Once all Windows maintenance is applied, I believe another complete removal of the partial install of Sonar that had failed should be done, prior to attempting another install.
 
Bob Bone
 

I waited for a response from tech support on the issue before acting on your suggestions Bob Bone, but as the preliminary suggestion from Cakewalk was just to disable start up programs I must admit I didn’t harbor much hope. However, I decided to do this anyway, and at the same time do the Windows update thing.
 
X3 finally installed.
 
As I had already, long ago, stripped my start up programs down to just my Fireface 800 and my Midi controller (oh, and I had “Microsoft IntelliType Pro” at start up because a tech friend of mine told me—rightly or wrongly?—to best keep that one activated), I doubt that disabling these was the solution. I rather think it was the windows update that did the trick.
 
So thank you all for your advice and support. This forum has taken me beyond an impasse yet again.