You'll probably find that Sonar 4 projects open in the new version but obviously new versions might not open in Sonar 4.

In any case it's quite likely that Sonar 4 will run in Win 10. I had Sonar 6 run on Win 8.1 in compatibility mode.

You won't lose anything by trying. All Sonar versions coexist side by side quite happily. Just make sure to install the oldest one first so it doesn't override existing files.

mileskb
 
Regarding the TW stuff, it's not really a matter of good or not.  I'm sure there's something current that will outclass it, but problem is...  It's what was used so if I try to open any of that era projects, and it's not available, I loose 100's of hours of mastering work.
 
...more the "what do I do with the 100's of buns I have now that were all created on older technology?"  I later got into the habit of creating both final raw and processed tracks before mastering just in case something happened so that will help with some stuff.  I wouldn't expect new projects to be an issue.

As scook mentioned above, in order to access 32bit DX plugins (including the Timeworks plugs) you'll need to install the 32bit version of SONAR.   You can have the 32bit and 64bit versions of SONAR installed side by side, using the 32bit version to access old projects and the 64bit version for new(er) projects.

stevec
 
As scook mentioned above, in order to access 32bit DX plugins (including the Timeworks plugs) you'll need to install the 32bit version of SONAR.   You can have the 32bit and 64bit versions of SONAR installed side by side, using the 32bit version to access old projects and the 64bit version for new(er) projects.

Is there any real advantage to the 64 bit version?  I know what it says on paper, but the reality is, 32 bit programs tend to run better/faster than their 64 bit counterparts, especially on a 64 bit operating system.  Specific programs I use such as MS Office programs or more heavy lifting with Photoshop, the 32 bit versions load and run noticeably faster and are more stable.  As I used to consistently record 8 tracks at once on an old XP machine with 8 GB of RAM, I'm thinking I might be better suited to run the 32bit version and then I can at least run most of my old plugins at least until I can replace them if necessary with newer ones.  
 
It also appears that this is my old account as I see my Sonar ver 3 is listed in "My Software" from 2003.  Not sure why 4 isn't listed.   
 
Again, thanks for the insights..

Does anyone have access to the Timeworks plugins as standalone files.  They were bundled with Sonar 2.0 XL I believe, but I can't seem to get around the Direct X 8.1 check that halts the install of 2.0 XL.

This might get it installed for you.
 
http://www.cakewalk.com/Support/Knowledge-Base/2007013224/DirectX-9-Installation-Problems

mileskb

stevec
 
As scook mentioned above, in order to access 32bit DX plugins (including the Timeworks plugs) you'll need to install the 32bit version of SONAR.   You can have the 32bit and 64bit versions of SONAR installed side by side, using the 32bit version to access old projects and the 64bit version for new(er) projects.

Is there any real advantage to the 64 bit version?  I know what it says on paper, but the reality is, 32 bit programs tend to run better/faster than their 64 bit counterparts, especially on a 64 bit operating system.  Specific programs I use such as MS Office programs or more heavy lifting with Photoshop, the 32 bit versions load and run noticeably faster and are more stable.  As I used to consistently record 8 tracks at once on an old XP machine with 8 GB of RAM, I'm thinking I might be better suited to run the 32bit version and then I can at least run most of my old plugins at least until I can replace them if necessary with newer ones.  
 
It also appears that this is my old account as I see my Sonar ver 3 is listed in "My Software" from 2003.  Not sure why 4 isn't listed.   
 
Again, thanks for the insights..

You'll find it was a total waste of time using 8Gb of RAM on a 32 bit system - this is the GREAT limitation of a 32 bit system, it will only read 4Gb at best, in practice quite a bit less as the OS takes what it needs before Sonar is even loaded.
 
No, go 64 bit throughout and fit as much matching RAM as your motherboard will allow.
 
 

Thanks for the inputs and insights folks.   I am going to go 64bit...   
 
Interesting tidbit..  I'm actually reviving my old machine with a couple of hybrid drives as I don't want to setup a full new machine for another 6-9 months.  In the process, that old XP machine from my studio only had 2 GB RAM !?!?!
I routinely recorded 8 tracks, but really only when I did drums or tranfers to/from ADAT other than that is was just a couple at a time.  I recorded/mix and mastered several albums on that setup with a 200 mHZ AMD Processor and 2GB RAM using a Layla 24/96 interface.  
 
Anyway... all my old projects were recording on that machine without issue so I just need a new interface unfortunately and with new drives it should hold me just fine while I get my chops back up.
 
I was just really really surprised it had only 2GB of ram... but I guess that was a lot in 2005. Funny how we (at least me) sometimes take it for granted.
 
 

In hindsight, my old system (WinXP 32 bit) could and did run a 75 track project of Audio & Midi containing multiple, unbounced V-Vocal clips, extensive automation and a vast quantity of fx plugs, all without even blinking.
 
So I'm not going to knock the platform for what it was, it's just that things have moved on, mostly for the better, and it's a 64 bit world of computers laden with 32/64 Gb RAM

Bristol_Jonesey
it's just that things have moved on, mostly for the better, and it's a 64 bit world of computers laden with 32/64 Gb RAM

True dat !!!  Just funny to think about.  My first MIDI projects were on a Commodore64, first automated gig using MIDI was with an old IBM PS/2, amber screen etc..  LOL..  
 
No matter how fast they make computers, and how much ram they have...  the absolute fastest you can record a 3.5 minute track in real time is...... 3.5 minutes..  and the fastest you can listen to it in real time is...   also 3.5 minutes.
 
 

Same here - WinXP with 2GB RAM ran lots of projects loaded with audio tracks + plugins, and MIDI tracks mostly using outboard gear.
 
However, when it comes to VST instruments that's a different story...  loading an instance or two of Kontakt using a relatively modern orchestral library (or really anything) would quickly show just where those 32bit limitations lie.