I can't register my product. It's old, I bought it years ago, and now it won't load because it cannot be registered. There is ZERO customer support from what I can find, and the e-mail system is down. Does this company still exist?

No, it does not. Read the stickies in front of you.  Nor should you expect any support for a 12 year old piece of software. 

The company you purchased it from no longer exists. In fact, Cakewalk has been owned by at least two companies since your purchased it and now another company owns the software. They have only just taken over and are still transitioning so no sales etc. just yet.
 
The version you have is very old and so is no longer supported. Your best bet would be to wait a week or two until the new owners have got the online store back up, and then you can purchase an up to date version that will work.

Ricord1
I can't register my product. It's old, I bought it years ago, and now it won't load because it cannot be registered.

 
Did you register it when you bought it?
 
I did, and I wrote the serial # and product registration code down in the DVD case.
 
Both are required to activate the program.  If you can access your Cakewalk account, look under 'My products' for these numbers.  They are still visible in my account.  If available, recommend you print the account page with serial numbers for future reference.
 

Ricord1
 
There is ZERO customer support from what I can find, and the e-mail system is down. Does this company still exist?
 

 
Technically no, the Cakewalk company was shut down by Gibson in November, and the assets were bought in February this year by BandLab.  See the sticky post for the announcement. >>> http://forum.cakewalk.com/Hello-from-BandLab-Updated-2132018-m3730905.aspx
 
You can create a BandLab account using the same email address as your Cakewalk account, if you want your account details to be migrated to take advantage of the free crossgrade offer that BandLab will offer to former Sonar users.

sharke
No, it does not. Read the stickies in front of you.  Nor should you expect any support for a 12 year old piece of software. 

That runs on XP. Ahh the good 'Ol days. When windows were windows

Ricord1
...it won't load because it cannot be registered...

 
When you say "load", do you mean "install"? If so, then that can't be exactly true. Sonar 6 can be installed without authorization and will be fully functional for 30 days, after which it won't run until you enter a registration code. Or do you mean that it is already installed from long ago and won't run now because you forgot to register it?

Hi, and welcome to this forum. All of the above information is correct, and needs answering. 
You need to give more information on your process for us to be able to help.
If you registered SONAR earlier, serial & activation code should be available at https://www.cakewalk.com/My-Account/Products
All the best.

Would not the OP need to do the Single Sign On that was required a few years ago for his account?

A few more details are needed, else we are just guessing. 
 
If the OP saved the registration code, then all set, no sign-on necessary. If the product was registered online, the registration code is tucked away in the account.  If locked out of the account, that may be another story.
 
When was the account created? Did the OP migrate it to the new Cakewalk account system a few years ago?

Seeing this about Sonar 6 prompted me to look back on my emails to see if I still had my email confirmation from when I bought it. Going back to see all my emails from Cakewalk back then (2006) was fun trip down memory lane.  I bought Sonar 6 from the Cakewalk store and after registering it they sent me an email with the registration code.  So, if a person cannot for some reason access their Cakewalk account maybe they can still have the email from back when they registered it.  But, if it was never registered probably isn't anything that can be done to install it.  I took a look at my Cakewalk products listed on my account.  I can't believe how many Cakewalk purchases I've made over the years!  I even bought Project5 and Project5 ver 2!