There's no need to reinstall nopCommerce
1. Run update.sql over your database
2. Remove all files from v2.0 except App_Data\Settings.txt and App_Data\InstalledPlugins.txt
3. Unzip v2.1
4. Copy back App_Data\Settings.txt and App_Data\InstalledPlugins.txt files
1. Run update.sql over your database
2. Remove all files from v2.0 except App_Data\Settings.txt and App_Data\InstalledPlugins.txt
3. Unzip v2.1
4. Copy back App_Data\Settings.txt and App_Data\InstalledPlugins.txt files
You may want to also retain the Images in the Content folder (thumbnails)?
The folks that are posting issues here seems to be trying to RUN the install to upgrade from 2.0 to 2.1. They just need to copy files and run the SQL script and everything SHOULD work fine (Unless they made customizations)