I don't know if any issues will be created by Windows 8, but assuming that Filemaker works on Windows 8 like it should, the file produced will be the same whether you use Filemaker 12 to convert it on your current version of windows or later after you update.
Thanks for your reply.
But for the installation, do I need to have FM 9 installed or can I just use the downloaded media and new key directly and perform a clean install with FM 12?
I "hate" to install OLD software... :-)
You will not need the FMP 9 application if you have converted the file to .fmp12 format--the format required for Filemaker 12.