Please understand,NetWeaver is not a server or system.
It is a framework,whci has got Enterprise Portal,Exchange Infrastructure,MDM,xAPPS etc to name a few.
Each of the above product requires a server and system configurations repectively.
I hope I am clear.
Please do reply.
Typically for EP it would be :
2 GR RAM,with 30-40GB HD,and with latest Windows SP`s and latest IE.
If the server is for Production incease the RAM accordingly.
For Portal RAM is very crucial,as SAPJ2EE Engine uses lot of RAM.
I hope this helps.
If yes,do award points.
Have a look at http://service.sap.com/quicksizing for exact figures on machine requirements.