Hi, this problem needs to be handled in two different areas: converting UIRs and portinog code back to 8.5.
As per UIR files, files written in CVI2009 cannot be opened in 8.5 natively: you will need to convert them so that they can be opened. This is possible only if you have not used any feature not present in CVI8.5. With an UIR file opened, go to Files >> Save as... and look into Save As field if you can switch back to 8.5. I hope you can but I cannot be sure since I have not installed 2009 yet. This is the very first thing to do since if you cannot convert the UIR porting the code has little interest.
If there isn't a direct option from 2009 to 8.5 you could try installing CVI9 evaluation version and execute the conversion in two steps: from 2009 to CVI9 and from this to 8.5.
In any case, examine the converted UIR files in 8.5 before uninstalling CVI2009 as some controls can result in different aspect and settings when converted (in some cases controls not present in the older versions are simply ignored when saving: this is the case for TAB control passed from version 8.5 to 7.1 where it doesn't exist).
The next step is to port the code back to 8.5. You should have no problem in directly compiling the source in the old environment, provided you have not used any of the feature CVI2009 or CVI9 introduced in the IDE. This table should help you in finding if there can be any incompatibilities.
If you happen to use any additional software like DAQmx or others, be sure it is installed in the older version as well as CVI2009: this can be a problem if you are planning to install 8.5 after installing 2009 on the same machine, as several packages install in the newer release found in the system, not considering previous versions. If this is your case put a note here as in some case it is possible to port the relevant files from the newer to the older release of CVI without running the installation program.
