Yeha, the easiest way is to create a new DB and reimport your hands:
http://www.holdemmanager.net/faq/afm...aspx?faqid=146
After that, just delete your old DB:
Start Menu
Find the PostgreSQL 8.3 group
Start "pgAdmin III"
Double click "PostgreSQL Database..." under Server (1)
Insert your password for the database, generally something like "postgrespass", you have set it when installing postgreSQL
Databases
Now you can see your old HM database
Right Click and select "Delete/Drop"
Information: Even if you reimport hands that were already imported, HM doesn't import it twice btw