Network and Server Perfomance

I am looking for a tool that i can use which will quickly show how stressed my server is getting over the course of a week.

Basically i want to start the application/tool and leave it running for a week. I want to see times when it is using more memory processing and network bandwidth

I want to monitor the local Network Card activity for the server > Memory & Processor
Anyone got any good applications which don’t take a lot of time to use and i can easily retrieve information