Just starting to work with all the Fx Chains that came with Platinum.  When I loaded a Craig Anderton Amp Sim,  I saw the chain used Guitar Rig 4.  My plig in was in parenthesis as I had unknowingly uninstalled Guitar Rig 4 and loaded my private upgrade to Guitar Rig 5.  Did SONAR or Platinum come with Guitar Rig 4?  How can I re install it?

The FX Chains bundled with Platinum use TH2 SONAR or Producer. The last version of SONAR to include a version of Guitar Rig was X1. Which FX Chain did you try?

GR4 LE came with SONAR X1. You can best re-install that via NI's "Service Center" (type that at the Windows Button), or should be here for the default install (C:\Program Files\Native Instruments\Service Center).
 
The Overview tab in the Service Center shows what is installed on your machine.
 
Which chain is using GR4 for the CA amp sims?

???
 
I thought they all used included PC modules and included Cake effects. As Mettulus mentioned GR4 has not been included since X1 (thankfully because it... well wasn't very good but I could use other words to describe it).
 
Anyway... you should be able to reinstall GR4 using the Custom install function of Sonar and unchecking everything except GR4 however you would have created a Native Instruments account to access GR4 anyway so that would still be in that account and likely still available there (although I ahv enever tried this).
 
If it is not in your NI account then a) you may not have registered it back then and were actually running the GR Lite version instead of GR4 or b) maybe NI removed it from your account in favor of GR5 in which case contact NI support and ask them to send a download link (be sure to have the reg # for GR4 that came with Sonar).
 
Still don't think those chains use GR at all but I have not tried them yet.

Don't be a hater Beepster! Guitar Rig is good 

It was pretty much the definitive sim for quite a while but I could never use it... until GR5. GR5 was like night and day and I'd still use it for certain things but TH2 has taken over most of my sim needs.
 
I do want to try out some stuff with GR5 in conjunction with TH2 though. I think GR5 has many specific models TH2 does not so I'm thinking of trying GR5's effects and heads then running them through TH2 cabs and mics. Could be interesting... or could fail miserably. Still gonna try. :-p
 
Kind of interested in checking out Rack11 too after listening to some demos.

I loaded the acoustic guitar Clean Air Fx Chain that used Guitar Rig 4
 

Ah... you combined your FX chain folders. That is an FX chain from X1, not Platinum. I still have mine separated, but that is not in the CA amp sims (I had to go digging when I couldn't find it initially).