Lucien,

did you try storing the encrypted date in the registry?

also

Assuming the application uses tables... would the tables persist after the application was uninstalled? You may achieve what you want by having a 'lastmodified' field on each record. At startup your application can "select min(lastmodified)..." and compare the timestamp with datetime(). If the user uninstalls and reinstalls the demo version they can't use any data they created before... which might be inconvenient enough for them to pay up.

It's hard to prevent determined people cracking your software so a combination of techniques is a good idea.

hth

Nigel