I'm afraid I have to confirm - you really need to upgrade to nworks 5. Version 4 of nworks does not support vCenter 4 / ESXi4.
You will find that, yes, in nworks 4 you are able to create a connection to vCenter 4.
You would probably see some performance metrics and some events coming through.
* you would miss many events, because the format of many event messages changed (therefore our v4 pattern-matching event policies would not work). Many events would fall to catch-all.
* you would not get new events, for example on fault-tolerant VMs and other new vCenter 4 features.
* if you created new topology objects such as Virtual Application (vApp), then this would break the nworks Collector topology-generation, probably causing all collection of data to fail.
Definitely recommend that you upgrade to nworks 5, if you now have a vCenter 4 environment.
The upgrade process really is not too complicated - and the new features of License Server, and automatic load-balanced monitoring job allocation, mean that v5 is much easier to set up and administer.
Let us know if we can help,
Vice President, Product Management