Running multiple versions of Acrobat Reader

Is there a way to get multiple versions of Acrobat Reader to run at the same time. We have some old legacy apps that require Acrobat Reader 4? We have created a thinapp package for Acrobat Reader 8 and it works great. However, we can not run both Acrobat Reader 4 and Acrobat Reader 8 (thinapp) at the same time. If Acrobat Reader 8 (thinapp) is running and you try to open Acrobat Reader 4, it opens Acrobat Reader 8. If I close Acrobat Reader 8 (thinapp), then we are able to open Acrobat Reader 4.  Any suggestions would be appreciated.