Vista - Alternatives to formatting HD and reinstalling Vista

I have a Vista Premium PC where I installed a trial version of a program,
let it expire and now I bought the full version but cannot seem to get it to
install since the ghost of the old trial version seems to be haunting my PC.

Before I start formatting the drive (and lose all my other programs and
settings) and attempt to reinstall Vista, I was wondering whether there was
some easy way to wipe all traces of the trial program? I am no great tech
expert, so protracted brain surgery with registry settings may not be an
option for me!

Ignoramus wrote:The people from whom you bought the licence for your application
are the people to ask about how to get rid of trial settings.