Hello everybody in the forum
I would much appreciate  if you could  help me   .
I did all my music compositions with virtual instruments using  Sonar 6 Producer edition on Windows XP. By personal circumstances  I had to stop with it and  I did not update to la latest Windows system and my  Sonar 6 files are in a Western Digital (WD) external hard disc. I have also Sonar LE installed  . So what to do now? How can I update all my work and bring it to Windows 10 and a into different Cakewalk music Production like Sonar Platinum? What are  my options once I buy a new music workstation with Windows 10?  Would I be able to open my Sonar 6 file in a different Windows system and Cakewalk music production like Platinum ?
Thanks very much.
Paco

Your Sonar 6 files should open in newer versions of Sonar. The real problem is outdated VST instruments (Synths) and DXI FX as well as VST-I's and FX that are no longer carried in newer versions of Sonar.
 
If your old Sonar 6 projects contained any VST-Instruments that are not longer included in Sonar Platinum than those tracks will come up blank as midi only and Sonar Platinum might complain about "Missing Plug ins".
 
My suggestion is to narrow down what Sonar 6 has and what Sonar Platinum has and either bounce down those midi tracks to audio or research which new plug ins to use from platinum.
One user mentioned a couple months ago that "Its a sad state of affairs if your projects have a 10 year shelf life".
Well its not the projects shelf life, its the ancient plug ins that are no longer accessible or simply don't work in newer versions of Windows and/or Sonar. I don't blame Cakewalk for that. If they kept updating every plug in ever made they wouldn't have time to create new ones and thus their product would be labeled "dated".

One thing I've encountered on opening up projects created on older versions of Sonar in the latest version of Platinum is I sometimes have to turn the track gain controls up and down to get the audio to play back at the proper volume. For example, at first the track volume would be peaking at -15... I turn the gain in track inspector off of zero and then back to zero and all of a sudden the track is peaking at -6 where I would have been recorded it in the first place. Once I adjust all of the gains and re-save the session, everything stays fine. It took me a while to figure out that fix.

@Chuckebaby: Thanks very much. Yes,I fully agree with your suggestions. I'll  find disappointing if I am not able to open those files with the already added FX,VST,etc  but probably Sonar Platinum has things alike those I used,everything can be changed,the foundation of everything is always the composition in itself,the score. This is  for me the down side of technology and for self taught musicians and composers,you need always to transfer your files to a different medium or format unless you can hand write your  music as the only possible way to preserve it for posterity and beyond.
Why shouldn't be possible to open any cakewalk project or at least  make them compatible with new Windows systems? I think the plugs ins should be  part of  a  Cakewalk sound library.
Once again thank you for your helpful answer.
 

Install the missing plug-ins from the old versions of SONAR. Install both 32 and 64bit Platinum on the same machine. When an old project has 32bit DX plug-ins use 32bit Platinum.

@scook  and @ rycatchemark Thanks very much

You might also want to consider if any external hardware you might have (ie audio interface) has compatible drivers for win 10. 
 
Also, IMHO win 10 sucks.