First - use the Windows 7 Firewall and Microsofts Security Essentials to keep the netbook safe. They should be pre-installed but if they aren't just download them from the Microsoft site.
After that it's up to you! If you want to Word Process or use Spreadsheets then OpenOffice is a VERY good alternative to Microsofts Office and it's FREE.
Choose the Browser carefully. I use Opera on my Netbook (I'm using it now) but Chrome or Firefox are also alternatives to Internet Explorer.
Basically you can use most programmes but Netbooks are less powerful than most modern laptops so might struggle with graphics heavy applications. Try and see what works, uninstalling is easy enough if you don't like any of them.