I have been experiencing some strange problems with Sonar7 (XP 32).  I want to try re-installing the software without risking the  loss any of my existing information.
 
What is the best way to do this?

Drag all your sonar folders to a back up drive. 
I never store my CWP and audio in the C drive, it's is stored in a few data drives. If I re intall my OS or even move to a different computer everything is there. I do have to drop all non Sonar VST dll's in the Sonar shared plug in folder, that's all. 
 

I installed a new drive and I would like to move all my audio and projects to this new drive.  What are the folders called in Sonar that I need to find this data?

Rossl
I installed a new drive and I would like to move all my audio and projects to this new drive.  What are the folders called in Sonar that I need to find this data?

 
These filepaths can be set in:
Options > Global Options > Folders

Oh my goodness, you don't know where your files are? that is living dangerously.
But it seems to be a common practice . With any software, word possessors, picture editing they all will store somewhere and you should be the one who points the way, not the computer. That's how data is lost.
As Kevv has pointed out the default in on C drive in the Sonar Folder.   

I completed the "re-install" no problems encountered.

Still seeing the issue described above.

Can I delete the user defined presets for a plug-in? Where would I find these files?

You didn't really describe the issue you were having. Just a vague reference to "strange problems".
Since re-installing Sonar did not correct the problem, that suggests the problem may not be directly related to Sonar.
It could be any number of things. System variables, corrupt plug-ins, user error, etc.
Your last question definitely raises a flag.
Please describe, in as much detail as possible, the problem(s) you are having.
 

The problem is with my user defined presets.  I had defined this in another tread and didn't get any responses, which is the reason why I was not describing it again.
 
I had an existing preset for VC_64.  I made some changes to the EQ only.  I saved the preset under a "new name". 
 
I moved on to another track..................when I went back to the track (with VC_64) I noticed it had the "original name" preset.  The "new name" was in the drop down menu so I clicked on the "new name".  The new name was displayed as the active preset.
 
I noticed that the EQ settings did not change when I went from the "original" to the "new" name.
 
I closed VC_64 and opened it again and it went back to the "original".
 
Unfortunately I don't remember which EQ settings are saved (because the change was very slight).
 
I noticed the same thing happened with a drum kit in Session Drummer 2.  I had a kit defined which I used as basis for a new kit in a new song.  I made numerous changes and saved them.  I closed and saved the project.  When I opened it again I noticed the new kit was no longer active and it reverted back to the original kit.....

In your other thread I mentioned that this might be caused by hidden data in the MIDI file. Are these your own MIDI tracks? 
Hidden data won't always show in the event view. 
 
Tricks you can try is change the channel of the track. 
Slip edit the beginning of the track which is where most PG and efx send info will hide. 
 
Try a different EQ plug in. that one might be buggy. I have this same thing happen with "Mr Tramp" The tremelo won't sty on, shuts off. 
 
Just some shots in the dark. 

These are not midi tracks.