Probably nothing...but I'm not taking any chances...the little yellow sticker containing what looks like my (rather lengthy) serial number for my X3Pro upgrade (boxed edition)...the one on the back of the first DVD...is all in German.  And guess what?  No, go on, guess.  I don't speak or read German...at least not more than a few cusswords and such.  So...is that, indeed, my serial number and do I have to do anything with it other than enter it when I'm installing X3? 
 
Again, this is the boxed edition I got from Sweetwater so I'm suspecting there's some sort of registration to my account at Cake involved and I want to make sure I'm doing the "right thing".
 
 

einfach toll! und warum nicht? Vielleicht kann ich Ihren Serialnummer haben um zu ueberpruefen?....
 
 
 
 
 
 
 
lol

lol maybe they've been like "yorolpal" ....mmm what a name this must be german .....double checking with NSA : yep he writes an strange english in forums .....ok german confirmed ....next !!

Yorolpal - DeinaltFreund....
 

Seriennummer, not Serialnummer, isn't it?
 
Your serial number should start with CXSP and then 15 digits.
 
Run the installer, it will ask you to input your serial number.  You will also need your Reg code from from your account page on cake shop site.  IIRC you will get this code after you have entered serial number, but it has been a while since I installed from disks.
 
 

yorolpal
Probably nothing...but I'm not taking any chances...the little yellow sticker containing what looks like my (rather lengthy) serial number for my X3Pro upgrade (boxed edition)...the one on the back of the first DVD...is all in German.  And guess what?  No, go on, guess.  I don't speak or read German...at least not more than a few cusswords and such.  So...is that, indeed, my serial number and do I have to do anything with it other than enter it when I'm installing X3? 
 
Again, this is the boxed edition I got from Sweetwater so I'm suspecting there's some sort of registration to my account at Cake involved and I want to make sure I'm doing the "right thing".
 
 

Ok, that was a mistake. But first off that's not your serial number, that's a redemption code.
 
Visit www.cakewalk.com/redeem
 
Enter your number from that sticker and you'll get your serial numbers and downloads as well. You will need your SONAR X2 Producer serial number to verify ownership. 

ok i had fun, but seriously to get someone from CW so quickly on this...it's nearly 23.00 here in the UK and so 18.00 in Boston...good stuff Andrew

Thanks Andrew, ol pal!  That did the trick!  Ach du Leiber!!

ACH...

yorolpal
the little yellow sticker containing what looks like my (rather lengthy) serial number for my X3Pro upgrade (boxed edition)...the one on the back of the first DVD...is all in German

Der Fuhrer will be pleased!