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RTC and VisualBasic 6.0
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How to successfully use RTC repository with old VB 6.0 projects?
RTC support Visual Studio 2005 and VS 2008. I assume that your VB6.0 is not in these version on VS.
I would suggest first migrate VB6.0 project to either VS2005 or VS2008 and then use RTC VS client to source control.
Please also take a look at http://jazz.net/library/article/117 section 4 on how to check-in any directory into Jazz respository.