Hi
It seems that with version 3.29 that when the "trial" period has expired you get a message to say you can either buy the software etc. or you can elect to continue to use it, with the understanding that some features will have become unusable. This usually meant (I am using the past tense here) a reduction in the number of export formats.. but I find in fact that it has come to include the inability to save your work as a project. i.e. the vpj file. This makes the software pretty useless from this point in time.
The expiry period also seemed to be very variable...from a few hours to several days.
If you uninstall the software from the control panel you can reload the original setup.exe file (if you have kept it) and it will run OK again. (At least until the "New" trial period has expired.)
If you have experience in such matters have a look at the HKEY Current User/Software/NCH Software/Videopad
Registration and Settings in the Widows registry.
Nat