sure you can have multiple Netbeans
IDE installed on the same machine.
even you can run them toghether as they use seperate home directory.
to find out more about netbeans home directories take a look at your user home dir /.netbeans/
you will find a 5.0 and a 5.5beta2 there.
in windows users home directory are located at :
e.g :
c:\Documents and Settings\YOUR_LOGIN_NAME