@TheSteven and @Cactus, thanks for your help!
I managed to install the old Sonar LE on my Windows 10 64 bit.
Next, like @TheSteven said, I installed the VSC under a different configuraton as 32 bits, that worked!
Now the old Sonar LE with the VSC works on the Windows 10 64 bit, so I can play all my songs and continue as I did. This is with the old version however, but it works for me.
Now I have also downloaded the trial version of Home Studio. I would prefer using this newer version as I like TTS-1 more. My intention was to use the old VSC plugin for playing the old songs, and using the TTS-1 for recording new songs.
For this, I see 3 options:
1. Using the old Sonar LE, playing the old songs with VSC, but using TTS-1 for recording new songs. This doesn't work. Sonar LE recognises the TTS-1, but when I select it, it says "Failed to insert DXi. The DXi may not be properly installed." So this option doesn't work, unless I manage to install TTS-1 for SONAR LE properly. I wouldn't know how.
2. Buying Sonar Home Studio, playing the old songs with VSC, but using TTS-1 for recording new songs. This doesn't seem to work. The old songs won't be played with VSC. I can find the Sound Canvas which I installed (32 bit) but it has a different name, so Sonar considers is at being a different plug-in. I.e. te output doesn't recognise the newly installed VSC as being the same as the VSC output in the CWP-file, they have different names. In all tracks, output is set at "EDIROL VSC 1", this was the name of the plug-in in the old Sonar LE program when recording. No sound. The "old VSC" is newly installed and can be found as a "new" plug-in under the name "SOUND Canvas VA 1".... So both "EDIROL VSC 1" and "SOUND Canvas VA 1" are mentioned as separate outputs, but when I choose "EDIROL VSC 1" there is nothing, and when I choose "SOUND Canvas VA 1" I get a sound, but I have to choose all the instruments for each track new. That makes no sense, then I could rather use TTS-1.
So question is: is there a way to substitute the "EDIROL VSC 1" in the output by the new "SOUND Canvas VA 1", i.e. telling the program to use Sound Canvas plug-in instead of Edirol VSC 1, with same instruments selection?
3. Third option is to use only the old Sonar LE. This would work, but I cannot use TTS-1 or any facilities of Home Studio. That would be a shame.
4. Fourth option would be to use Sonar LE for the old songs, and Sonar Home Studio for the new recordings. But then, if I would work or improve the old songs, I can only do this with VSC.
Option 3 would be the easiest solution, but if you have any idea to solve the other problems, I would like to change to Sonar Home Studio or Artist. At least, if they are still available....?? Can I still buy/download these products from Cakewalk?
I apologise if the explanation above is too messy or complicated, I hope you understand what I mean.
Thanks again, you are very helpful.